Hi Charlie, thanks for testing the fillets.

> It seems there are things that the Solids++ fillet can do that the ACIS can't. Will it be sticking around?

Yes, the switch between fillet libraries will be staying for quite a while.

There are some cases where Solids++ can generate a fillet where ACIS can't, mainly on things where the fillet is trying to go around a bend that is smaller than the fillet radius. Solids++ can slice out that self intersecting fillet area if it's not too complicated, but ACIS won't do those cases.

But your case here looks more like a bug in MoI's conversion to and from ACIS geometry, that is an area that I'm still actively working on. I'll add your file to my list to test with.

With the attached version I replaced 2 of the planes and it's working ok on this one.

- Michael