Many thanks to Gael Langevin, the creator of the InMoov 3D-printed robot (http://www.inmoov.fr).
This post is a modification of the front skull, which originally consists of 4 parts. The goal was a continuous forehead. The 4 parts were put together, the surface was smoothed and then I made a transversal cut.
The holes on top where removed, because there are not needed anymore. The connectors were redesigned to also give support when printing.