The original GoPro mount is designed to mount the GoPro center mass and NOT center lens. This design fixes that problem for the people who want their GoPro lens aiming straight down whatever it is mounted to.
I made 2 versions; One is a pole mount and the other is more of a universal adapter for any mount.
Update: Added the bottom piece for the pole mount, it's not perfect but it'll do for now.
Use whatever infill you feel comfortable with the life of your gopro in the balance.... I used a high percent (90%) for safety. If you print the model with support, it should snap off easily with needle nose pliers.
You'll need to install a nut also, I used a 5mm-0.8 cap nut from home depot.