Using default Mach 3 Profile from https://www.langmuirsystems.com/downloads
Did not change motor tuning.
AutoCAD (in inches)
SheetCam tap (in inches)
SheetCam Machine Working Envelope set to X 25.3125" x Y 23.125"
Mach3 (in inches)
Mach3 using default profile from Langmuir downloads page
Test 6"x6" square… comes out a little over 7.5"
[Edit: Mach3 motor tuning is set to 16000 steps per on both X and Y as default from the downloaded setup.
Setting file scale in AutoCAD to 0.8 makes things a bit closer to reality.]