Hi ado, the kind of odd looking lumpy shaping comes from using the MOI SubD converter on a mesh that has not been set up for sub-d smoothing.

Here's some examples of how the control mesh should be formed for sub-d smoothing to make a good quality result:
https://www.youtube.com/watch?v=ckOTl2GcS-E

- Michael

I have more detailed stuff via a 50MB Alibre Stp

Which converts to a 75MB MOI stp (about 10 mins)
and a 132MB 3dm file (a few minutes)

It's the processing time for these things when you're just experimenting, it starts to get silly pretty quickly

If you're getting money for a job no doubt it's worth more hassle