Alright, my findings: First of all, I decided to use the model from https://community.fxtec.com/profile/8210-ubuntuscofield/ (and only the bottom part, because I intend to use it in a leather book case) instead of the one referenced in this thread. The person printing it for me used the FLEX filament, that was OK (in fact, he printed another using PLA and yet another using PETg as well, but only the FLEX filament ended up in something usable). However, I had to adapt (enlarge) several of the holes a bit - in particular the two speaker holes (both had to be extended a bit towards the middle), t