Hi Patrick, your result looks great! Yup sometimes when the "automatic" type processes fail or get confused your best bet is to just manually construct a cutting piece and "do it yourself".

I think the fix to the UV trim curve generation with the latest geometry library should probably be a big help in general for robustness, there were a couple of different bugs in that area causing mangled boundaries that could happen in a variety of different operations.

It looks like I've tracked down the area of the library that changed that made the final boolean step of the shell not work quite correctly with the updated library, so I can undo that particular change but keep the other fixes.

That's one thing that's really pretty frustrating about the geometry library being updated, it's not unusual for some things that get changed to help out in one particular case but then cause problems in other cases...

I was going to wait until cramming in a couple of more features before releasing a new beta, but I think that maybe I'll go ahead and roll one out now, the geometry library update and an update to Network are enough to merit a new release now I guess, I will try to roll out one later tonight.

In that new release the 0.5mm thick shell of your original posted file should then work ok.

Thanks for posting the example file so I could test with it!

- Michael