Hi sneather, you could also try ViaCAD for importing the STEP file, I'm pretty sure they have a Mac version. If things behave pretty differently between MoI and ViaCAD for the import then that could mean something needs to be tuned up in MoI. If they behave the same then it's pretty likely to be just how the file is set up.

Is the 3DM file you posted one that is at the import scale that you're talking about or did you scale that up already?

- Michael