I have my settings set to inches but when saved as STL format, it turns to mm. This causes other programs to not read in the file correctly. Any suggestions?

I use MeshCAM V5 to convert a part into G Code.  This is then sent to my CNC router to cut the part out.  I have used other 2D drawing programs with no issues but when I use PTC it creates a very large part.  After looking at the scale difference, I found that it is exactly the scale difference of converting inches to mm.  Any idea why?  Thanks in advance.