Hi.

I use SU for 3D printing. I find that when working at small scale such as 1:87, some things that one would expect should work in SU, doesn't. if I enlarge everything at least 10 or 100 times, SU works a lot better. I then re shrink by the same factor before exporting to STL for printing. 1000x is a good value, as I can treat millimetres as metres.
It's nice to be able to suggest solutions than to be the one asking for them!
Steve