Hi Martin, Insert uses solid/extended offsetting and there are a lot of situations where the extension mechanism in the geometry library can just get confused.

So I wouldn't be surprised if you're running into some limitation involving offsetting more than any particular problem that you are doing wrong yourself. I will take a look at your file and your screencast though to see if I can give you any tips.

Basically though Inset tries to bundle up several offset and boolean operations and if it is not able to get a result for you, you may need to do some a more sort of "low level" construction method constructing individual pieces or surfaces yourself by stuff like offsetting only one surface at a time and building extension areas manually, etc...

- Michael