Hi Lewis, well different positions can definitely be handled by instancing...

But another possible thing is that often times STP files will only contain the 3D curves for trimming boundaries, and MoI uses a combination of both 3D edges and UV space edges for every trimming boundary edge. It could be possible that those newly created UV trim edges are what increases your file size.

But that's just another guess, if you want to send me the file at moi@moi3d.com (you'll need to send a link to a file sharing service like dropbox or similar), I could try to take a look and possibly give a more definitive answer.

- Michael