Having sweated for years with Rhino first and then MoI trying to loft complex ship hull shapes and the sort, I have learned the hard way that it matters a lot to use the fewest, cleanest, simplest curves necessary to describe reasonably accurately the shape intended. It pays also not to insist on generating the whole shape at once if getting into trouble, but to go for parts that can be welded later (with continuity issues, my pet peeve, as a consequence). These days, I spend way more time optimising the curves than generating the surfaces and volumes, and it pays handsomely.

I do not get the impression that MoI is a let down in this matter, nor in any other for that. Simply I wish there would be tools to assess curvature and continuity, to rebuild curves, etc. But much of that is in Rhino that I always run in the background and is only one copy/paste away.