diff --git a/MatterControl.Printing/GCode/GCodeMemoryFile.cs b/MatterControl.Printing/GCode/GCodeMemoryFile.cs
index 8c9137a63..7bf5132a9 100644
--- a/MatterControl.Printing/GCode/GCodeMemoryFile.cs
+++ b/MatterControl.Printing/GCode/GCodeMemoryFile.cs
@@ -942,6 +942,11 @@ namespace MatterControl.Printing
 			return false;
 		}
 
+		/// <summary>
+		/// Get the height of this layer (from the top of the previous layer to the top of this layer).
+		/// </summary>
+		/// <param name="layerIndex"></param>
+		/// <returns></returns>
 		public override double GetLayerHeight(int layerIndex)
 		{
 			if (layerHeights.Count > 0)
@@ -962,6 +967,11 @@ namespace MatterControl.Printing
 			return .5;
 		}
 
+		/// <summary>
+		/// Get the height of the top of this layer as measure from the bed
+		/// </summary>
+		/// <param name="layerIndex"></param>
+		/// <returns></returns>
 		public override double GetLayerTop(int layerIndex)
 		{
 			double total = 0;
@@ -972,6 +982,21 @@ namespace MatterControl.Printing
 			return total;
 		}
 
+		/// <summary>
+		/// Get the height of the bottom of this layer as measure from the bed
+		/// </summary>
+		/// <param name="layerIndex"></param>
+		/// <returns></returns>
+		public double GetLayerBottom(int layerIndex)
+		{
+			double total = 0;
+			for (int i = 0; i < layerIndex; i++)
+			{
+				total += GetLayerHeight(i);
+			}
+			return total;
+		}
+
 		public override int GetLayerIndex(int instructionIndex)
 		{
 			if (instructionIndex >= 0
diff --git a/MatterControlLib/PartPreviewWindow/PrinterTabPage.cs b/MatterControlLib/PartPreviewWindow/PrinterTabPage.cs
index 273cefaa9..1fcfb3277 100644
--- a/MatterControlLib/PartPreviewWindow/PrinterTabPage.cs
+++ b/MatterControlLib/PartPreviewWindow/PrinterTabPage.cs
@@ -461,11 +461,10 @@ namespace MatterHackers.MatterControl.PartPreviewWindow
 		{
 			var bodyRow = new GuiWidget()
 			{
-				HAnchor = HAnchor.Fit | HAnchor.Center,
+				HAnchor = HAnchor.Stretch,
 				VAnchor = VAnchor.Top | VAnchor.Fit,
 				//BackgroundColor = new Color(theme.Colors.PrimaryBackgroundColor, 128),
 				MinimumSize = new Vector2(275, 140),
-				Selectable = false
 			};
 
 			// Progress section
@@ -477,9 +476,8 @@ namespace MatterHackers.MatterControl.PartPreviewWindow
 
 			var progressContainer = new FlowLayoutWidget(FlowDirection.TopToBottom)
 			{
-				Margin = new BorderDouble(50, 0),
 				VAnchor = VAnchor.Center | VAnchor.Fit,
-				HAnchor = HAnchor.Center | HAnchor.Fit,
+				HAnchor = HAnchor.Stretch,
 			};
 			expandingContainer.AddChild(progressContainer);
 
@@ -491,12 +489,88 @@ namespace MatterHackers.MatterControl.PartPreviewWindow
 			};
 			progressContainer.AddChild(progressDial);
 
+			var bottomRow = new GuiWidget()
+			{
+				HAnchor = HAnchor.Stretch,
+				VAnchor = VAnchor.Fit
+			};
+			progressContainer.AddChild(bottomRow);
+
 			var timeContainer = new FlowLayoutWidget()
 			{
 				HAnchor = HAnchor.Center | HAnchor.Fit,
 				Margin = 3
 			};
-			progressContainer.AddChild(timeContainer);
+			bottomRow.AddChild(timeContainer);
+
+			// we can only reslice on 64 bit, because in 64 bit we always have the gcode loaded
+			if (IntPtr.Size == 8)
+			{
+				var resliceButton = new TextButton("Re-Slice", theme)
+				{
+					HAnchor = HAnchor.Right,
+					VAnchor = VAnchor.Center,
+					Margin = new BorderDouble(0, 0, 7, 0)
+				};
+				bool activelySlicing = false;
+				resliceButton.Click += (s, e) =>
+				{
+					resliceButton.Enabled = false;
+					UiThread.RunOnIdle(async () =>
+					{
+						if (!activelySlicing
+							&& printer.Settings.IsValid()
+							&& printer.Bed.EditContext.SourceItem != null)
+						{
+							activelySlicing = true;
+							if (bottomRow.Name == null)
+							{
+								bottomRow.Name = printer.Bed.EditContext.GCodeFilePath;
+							}
+							await ApplicationController.Instance.Tasks.Execute("Saving".Localize(), printer.Bed.SaveChanges);
+							// start up a new slice on a backgroud thread
+							await ApplicationController.Instance.SliceItemLoadOutput(
+								printer,
+								printer.Bed.Scene,
+								printer.Bed.EditContext.GCodeFilePath);
+							// Switch to the 3D layer view if on Model view
+							if (printer.ViewState.ViewMode == PartViewMode.Model)
+							{
+								printer.ViewState.ViewMode = PartViewMode.Layers3D;
+							}
+							// when it is done queue it to the change to gcode stream
+							var message2 = "Would you like to switch to the new G-Code? Before you switch, check that your are seeing the changes you expect.".Localize();
+							var caption2 = "Switch to new G-Code?".Localize();
+							StyledMessageBox.ShowMessageBox(async (clickedOk2) =>
+							{
+								if (clickedOk2)
+								{
+									if (printer.Connection != null
+										&& (printer.Connection.PrinterIsPrinting || printer.Connection.PrinterIsPaused))
+									{
+										printer.Connection.SwitchToGCode(printer.Bed.EditContext.GCodeFilePath);
+										bottomRow.Name = printer.Bed.EditContext.GCodeFilePath;
+									}
+								}
+								else
+								{
+									await ApplicationController.Instance.SliceItemLoadOutput(
+										printer,
+										printer.Bed.Scene,
+										bottomRow.Name);
+								}
+								activelySlicing = false;
+								resliceButton.Enabled = true;
+							}, message2, caption2, StyledMessageBox.MessageType.YES_NO, "Switch".Localize(), "Cancel".Localize());
+						}
+						else
+						{
+							resliceButton.Enabled = true;
+						}
+					});
+				};
+				bottomRow.AddChild(resliceButton);
+			}
 
 			timeContainer.AddChild(new ImageWidget(AggContext.StaticData.LoadIcon("fa-clock_24.png", theme.InvertIcons))
 			{
diff --git a/MatterControlLib/PrinterCommunication/Io/GCodeSwitcher.cs b/MatterControlLib/PrinterCommunication/Io/GCodeSwitcher.cs
new file mode 100644
index 000000000..457b4fdf4
--- /dev/null
+++ b/MatterControlLib/PrinterCommunication/Io/GCodeSwitcher.cs
@@ -0,0 +1,141 @@
+/*
+Copyright (c) 2015, Lars Brubaker
+All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are met:
+
+1. Redistributions of source code must retain the above copyright notice, this
+   list of conditions and the following disclaimer.
+2. Redistributions in binary form must reproduce the above copyright notice,
+   this list of conditions and the following disclaimer in the documentation
+   and/or other materials provided with the distribution.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
+ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
+ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+The views and conclusions contained in the software and documentation are those
+of the authors and should not be interpreted as representing official policies,
+either expressed or implied, of the FreeBSD Project.
+*/
+
+using MatterControl.Printing;
+using MatterHackers.VectorMath;
+using System.Threading;
+using System.Threading.Tasks;
+
+namespace MatterHackers.MatterControl.PrinterCommunication.Io
+{
+	public class GCodeSwitcher : GCodeStream
+	{
+		private GCodeMemoryFile switchToGCode = null;
+		PrinterConnection printerConnection;
+
+		public GCodeSwitcher(string gcodeFilename, PrinterConnection printerConnection, int startLine = 0)
+		{
+			this.printerConnection = printerConnection;
+			var fileStreaming = GCodeFile.Load(gcodeFilename,
+					new Vector4(),
+					new Vector4(),
+					new Vector4(),
+					Vector4.One,
+					CancellationToken.None);
+
+			this.GCodeFile = fileStreaming;
+			LineIndex = startLine;
+		}
+
+		public GCodeFile GCodeFile { get; private set; }
+		public int LineIndex { get; private set; } = -1;
+
+		public override void Dispose()
+		{
+		}
+
+		public override string ReadLine()
+		{
+			if (LineIndex < GCodeFile.LineCount)
+			{
+				if (LineIndex > 1
+					&& GCodeFile is GCodeMemoryFile currentMemoryFile)
+				{
+					if (switchToGCode != null)
+					{
+						var prevlayerIndex = currentMemoryFile.GetLayerIndex(LineIndex - 1);
+						var layerIndex = currentMemoryFile.GetLayerIndex(LineIndex);
+						// we only try to switch as we are changing layers
+						if (prevlayerIndex < layerIndex)
+						{
+							var currentBottom = currentMemoryFile.GetLayerBottom(layerIndex);
+							// see if there is a layer height that is compatible in the new gcode
+							for (int i = 0; i < switchToGCode.LayerCount; i++)
+							{
+								// find the first layer in the new code that is greater than or eaqual to our current height
+								var switchBottom = switchToGCode.GetLayerBottom(i);
+								if (switchBottom >= currentBottom)
+								{
+									// is the current gcode the same or bigger than the new gcode
+									if (currentBottom >= switchBottom)
+									{
+										// switch the first time we can
+										GCodeFile = switchToGCode;
+										LineIndex = switchToGCode.GetFirstLayerInstruction(i);
+										printerConnection.QueueLine($"G92 E{switchToGCode.Instruction(LineIndex).EPosition}", true);
+										switchToGCode = null;
+									}
+									else // only switch if we are within one layer height of the new gcode
+									{
+										if(currentBottom - switchBottom < switchToGCode.GetLayerHeight(layerIndex))
+										{
+											GCodeFile = switchToGCode;
+											LineIndex = switchToGCode.GetFirstLayerInstruction(i);
+											printerConnection.QueueLine($"G92 E{switchToGCode.Instruction(LineIndex).EPosition}", true);
+										}
+									}
+									// we are done evaluating after the first found layer
+									break;
+								}
+							}
+						}
+					}
+				}
+				return GCodeFile.Instruction(LineIndex++).Line;
+			}
+
+			return null;
+		}
+
+		public override void SetPrinterPosition(PrinterMove position)
+		{
+		}
+
+		public void SwitchTo(string gcodeFilename)
+		{
+			if (GCodeFile is GCodeMemoryFile)
+			{
+				Task.Run(() =>
+				{
+					var switchToGCode = GCodeFile.Load(gcodeFilename,
+							new Vector4(),
+							new Vector4(),
+							new Vector4(),
+							Vector4.One,
+							CancellationToken.None);
+
+					if (switchToGCode is GCodeMemoryFile memoryFile)
+					{
+						this.switchToGCode = memoryFile;
+					}
+				});
+			}
+		}
+	}
+}
\ No newline at end of file
diff --git a/MatterControlLib/PrinterCommunication/Io/PrintRecoveryStream.cs b/MatterControlLib/PrinterCommunication/Io/PrintRecoveryStream.cs
index d1070623b..5b98b97d4 100644
--- a/MatterControlLib/PrinterCommunication/Io/PrintRecoveryStream.cs
+++ b/MatterControlLib/PrinterCommunication/Io/PrintRecoveryStream.cs
@@ -38,7 +38,7 @@ namespace MatterHackers.MatterControl.PrinterCommunication.Io
 
 	public class PrintRecoveryStream : GCodeStream
 	{
-		private GCodeFileStream internalStream;
+		private GCodeSwitcher internalStream;
 		private double percentDone;
 		double recoverFeedRate;
 		PrinterMove lastDestination;
@@ -48,7 +48,7 @@ namespace MatterHackers.MatterControl.PrinterCommunication.Io
 		public RecoveryState RecoveryState { get; private set; } = RecoveryState.RemoveHeating;
 		private PrinterConfig printer;
 
-		public PrintRecoveryStream(PrinterConfig printer, GCodeFileStream internalStream, double percentDone)
+		public PrintRecoveryStream(PrinterConfig printer, GCodeSwitcher internalStream, double percentDone)
 		{
 			this.printer = printer;
 			this.internalStream = internalStream;
diff --git a/MatterControlLib/PrinterCommunication/PrinterConnection.cs b/MatterControlLib/PrinterCommunication/PrinterConnection.cs
index a3d90967b..63555a820 100644
--- a/MatterControlLib/PrinterCommunication/PrinterConnection.cs
+++ b/MatterControlLib/PrinterCommunication/PrinterConnection.cs
@@ -184,7 +184,7 @@ namespace MatterHackers.MatterControl.PrinterCommunication
 
 		private PrinterMove lastReportedPosition;
 
-		private GCodeFileStream gCodeFileStream0 = null;
+		private GCodeSwitcher gCodeFileSwitcher0 = null;
 		private SendProgressStream sendProgressStream1 = null;
 		private PauseHandlingStream pauseHandlingStream2 = null;
 		private QueuedCommandsStream queuedCommandStream3 = null;
@@ -513,6 +513,11 @@ namespace MatterHackers.MatterControl.PrinterCommunication
 			}
 		}
 
+		public void SwitchToGCode(string gCodeFilePath)
+		{
+			gCodeFileSwitcher0.SwitchTo(gCodeFilePath);
+		}
+
 		public string ComPort => printer.Settings?.Helpers.ComPort();
 
 		public string DriverType => (this.ComPort == "Emulator") ? "Emulator" : printer.Settings?.GetValue("driver_type");
@@ -542,9 +547,9 @@ namespace MatterHackers.MatterControl.PrinterCommunication
 		{
 			get
 			{
-				if (gCodeFileStream0 != null)
+				if (gCodeFileSwitcher0 != null)
 				{
-					return gCodeFileStream0?.GCodeFile?.GetLayerIndex(gCodeFileStream0.LineIndex) ?? -1;
+					return gCodeFileSwitcher0?.GCodeFile?.GetLayerIndex(gCodeFileSwitcher0.LineIndex) ?? -1;
 				}
 
 				return -1;
@@ -597,9 +602,9 @@ namespace MatterHackers.MatterControl.PrinterCommunication
 					return 100.0;
 				}
 				else if (NumberOfLinesInCurrentPrint > 0
-					&& gCodeFileStream0?.GCodeFile != null)
+					&& gCodeFileSwitcher0?.GCodeFile != null)
 				{
-					return gCodeFileStream0.GCodeFile.PercentComplete(gCodeFileStream0.LineIndex);
+					return gCodeFileSwitcher0.GCodeFile.PercentComplete(gCodeFileSwitcher0.LineIndex);
 				}
 				else
 				{
@@ -714,12 +719,12 @@ namespace MatterHackers.MatterControl.PrinterCommunication
 		{
 			get
 			{
-				if (gCodeFileStream0?.GCodeFile == null)
+				if (gCodeFileSwitcher0?.GCodeFile == null)
 				{
 					return 0;
 				}
 
-				return gCodeFileStream0.GCodeFile.Ratio0to1IntoContainedLayer(gCodeFileStream0.LineIndex);
+				return gCodeFileSwitcher0.GCodeFile.Ratio0to1IntoContainedLayer(gCodeFileSwitcher0.LineIndex);
 			}
 		}
 
@@ -754,22 +759,22 @@ namespace MatterHackers.MatterControl.PrinterCommunication
 			}
 		}
 
-		public int TotalLayersInPrint => gCodeFileStream0?.GCodeFile?.LayerCount ?? -1;
+		public int TotalLayersInPrint => gCodeFileSwitcher0?.GCodeFile?.LayerCount ?? -1;
 
-		private int NumberOfLinesInCurrentPrint => gCodeFileStream0?.GCodeFile?.LineCount ?? -1;
+		private int NumberOfLinesInCurrentPrint => gCodeFileSwitcher0?.GCodeFile?.LineCount ?? -1;
 
 		public int TotalSecondsInPrint
 		{
 			get
 			{
-				if (gCodeFileStream0?.GCodeFile?.LineCount > 0)
+				if (gCodeFileSwitcher0?.GCodeFile?.LineCount > 0)
 				{
 					if (this.FeedRateRatio != 0)
 					{
-						return (int)(gCodeFileStream0.GCodeFile.TotalSecondsInPrint / this.FeedRateRatio);
+						return (int)(gCodeFileSwitcher0.GCodeFile.TotalSecondsInPrint / this.FeedRateRatio);
 					}
 
-					return (int)(gCodeFileStream0.GCodeFile.TotalSecondsInPrint);
+					return (int)(gCodeFileSwitcher0.GCodeFile.TotalSecondsInPrint);
 				}
 
 				return 0;
@@ -2031,7 +2036,7 @@ namespace MatterHackers.MatterControl.PrinterCommunication
 
 		private void ClearQueuedGCode()
 		{
-			gCodeFileStream0?.GCodeFile?.Clear();
+			gCodeFileSwitcher0?.GCodeFile?.Clear();
 		}
 
 		private void DonePrintingSdFile(object sender, FoundStringEventArgs e)
@@ -2096,24 +2101,19 @@ namespace MatterHackers.MatterControl.PrinterCommunication
 			GCodeStream firstStreamToRead = null;
 			if (gcodeFilename != null)
 			{
-				gCodeFileStream0 = new GCodeFileStream(GCodeFile.Load(gcodeFilename,
-					new Vector4(),
-					new Vector4(),
-					new Vector4(),
-					Vector4.One,
-					CancellationToken.None));
+				gCodeFileSwitcher0 = new GCodeSwitcher(gcodeFilename, this);
 
 				if (this.RecoveryIsEnabled
 					&& activePrintTask != null) // We are resuming a failed print (do lots of interesting stuff).
 				{
-					sendProgressStream1 = new SendProgressStream(printer, new PrintRecoveryStream(printer, gCodeFileStream0, activePrintTask.PercentDone));
+					sendProgressStream1 = new SendProgressStream(printer, new PrintRecoveryStream(printer, gCodeFileSwitcher0, activePrintTask.PercentDone));
 					// And increment the recovery count
 					activePrintTask.RecoveryCount++;
 					activePrintTask.Commit();
 				}
 				else
 				{
-					sendProgressStream1 = new SendProgressStream(printer, gCodeFileStream0);
+					sendProgressStream1 = new SendProgressStream(printer, gCodeFileSwitcher0);
 				}
 
 				pauseHandlingStream2 = new PauseHandlingStream(printer, sendProgressStream1);
@@ -2121,7 +2121,7 @@ namespace MatterHackers.MatterControl.PrinterCommunication
 			}
 			else
 			{
-				gCodeFileStream0 = null;
+				gCodeFileSwitcher0 = null;
 				firstStreamToRead = new NotPrintingStream();
 			}
 
@@ -2167,12 +2167,12 @@ namespace MatterHackers.MatterControl.PrinterCommunication
 				double secondsSinceStartedPrint = timeSinceStartedPrint.Elapsed.TotalSeconds;
 
 				if (timeSinceStartedPrint.Elapsed.TotalSeconds > 0
-					&& gCodeFileStream0 != null
+					&& gCodeFileSwitcher0 != null
 					&& (secondsSinceUpdateHistory > secondsSinceStartedPrint
 					|| secondsSinceUpdateHistory + 1 < secondsSinceStartedPrint
-					|| lineSinceUpdateHistory + 20 < gCodeFileStream0.LineIndex))
+					|| lineSinceUpdateHistory + 20 < gCodeFileSwitcher0.LineIndex))
 				{
-					double currentDone = gCodeFileStream0.GCodeFile.PercentComplete(gCodeFileStream0.LineIndex);
+					double currentDone = gCodeFileSwitcher0.GCodeFile.PercentComplete(gCodeFileSwitcher0.LineIndex);
 					// Only update the amount done if it is greater than what is recorded.
 					// We don't want to mess up the resume before we actually resume it.
 					if (activePrintTask != null
@@ -2190,7 +2190,7 @@ namespace MatterHackers.MatterControl.PrinterCommunication
 						//timer.Restart();
 					}
 					secondsSinceUpdateHistory = secondsSinceStartedPrint;
-					lineSinceUpdateHistory = gCodeFileStream0.LineIndex;
+					lineSinceUpdateHistory = gCodeFileSwitcher0.LineIndex;
 				}
 
 				Thread.Sleep(5);