I have a bicycle helmet with a central vent, so an adhesive mount won't put the camera in the center. Also I don't trust adhesives, especially since I ride all year in temps well below zero.

The SCAD file contains a module that makes the basic rails you need to attach one of the standard mounts. This version has the zip tie mount, but you can put whatever base you like on it.

INSTRUCTIONS:
I printed with support (using Slic3r) to keep the overhangs from sagging too much. The easiest way I found to remove it was with a small flat blade screwdriver.
A little trimming/filing may be necessary to get the mount moving smoothly.
I found that using the stock mount plus just one arm from the helmet mount was plenty of articulation, the full helmet mount is more than is needed and puts the camera far enough forward that it feels awkward (and probably gives more chance to snag on stuff if you're riding offroad).