MakerBot Print is our newest print-prepration software, which supports native CAD files and STL assemblies,
allows you to interact with all your printers via the Cloud, and many other exciting new features.
@VeryWetPaint these are two very good solutions. maybe I overcomplicated it by trying to inset it. My goal was back then to have a constant wall thickness so that it would always extrude exactly 2walls for the whole labyrinth. but now that the printing quality increased so much by using a stepper based extruder this workaround is no longer needed and a scaled version on the inside works just as well and should also speed up the openscad rendering time :)