After suffering a number of failures of "Roll Cage Swivel Mount for GoPro" (https://www.thingiverse.com/thing:44997), I designed a MUCH STRONGER version with the same functionality, but with two key improvements. 1) The new base component is longer and has an extra pair of zip tie races. Also, the recessed races hold the ties in place quite well. 2) The original post design had a single layer providing all of the strength at the post/base interface. Inter-layer adhesion failures were common at this point. My design has a conical shaped post, with a much larger surface across which to transfer the load. As such, the new design is able to take much high G loads as is commonly found in high speed racing and stage rally competition.
See https://www.thingiverse.com/thing:1538262, for another mounting option.
I printed both the base and the post in the orientations shown. They do not need to be extremely accurate, just strong.