I designed this RAM Mount using a 5/16" 90mm long allen key cap screw to mount on the A Pillar of my Jeep JK Wrangler. I will be using it to hang a RAM style arm that will hold my phone holder/charger.
I printed this in ASA filament at 50mm/s 250 degrees and 100 degree print bed. I believe PLA would not be able to handle the heat in a vehicle environment.
Drawn in Sketchup 2017
I designed this in Sketchup 2017 and have attached the sketchup file for anyone who wants to modify the length of the mount for their own purposes.