Hi Marc, I'll try to think about that a little bit more.

I was thinking of possibly doing this option specifically for the booleans, but there are also other situations that can result in a multi-style solid like Join... So maybe it should be a more general kind of option that affects all solids that are created.

Also another way to get a multi-style solid is to just select one face out of the solid and set its style to something else. I don't think that I will try to disallow this one though.

- Michael