Per this discussion (http://moi3d.com/forum/messages.php?webtag=MOI&msg=8008.1), I'd like to request this feature in v4. The way I envision it working is, if I set units to inches within Moi, so I've created all my geometry in inches, but I'm exporting to a program that expects mm, selecting mm on export multiplies all dimensions (I think) by 25.4.