This so far is the most complex thing I have designed from scratch.
I had a need which was that Most GoPro mounts have a door or screw you have to open or undo to get the camera out, this usually means disassembling the rig entirely just to get the footage or replace the battery. This solves that problem (I was inspired by Devin from Make Anything who did a similar project for an older GoPro). Not having a top or door means the GoPro can just be lifted out of the rig and easily placed back in at will! And the best part is if you have a permanent rig set up on your 3D printer for time lapses, your shots will always look the same! This rig also keeps the back open to allow access to the screen on the hero 4 silver model and the side open to allow access to the micro SD card and for the camera to be plugged in without removing it. I'm really proud of this and if you make one I would really appreciate it if you posted a picture in the "I made one tab!"
I printed mine upside down
Post printing you should just be able to remove the supports and have no more cleanup. It should work straight away.
Side note- I'm unsure as to whether this will work for the other Hero 4 versions as I only have a Silver, and thus have only tested it on a Silver. But I see no reason why it shouldn't fit as the only major physical difference between models is the screen.
I grabbed a pair of calipers and first actually modeled out a 1:1 scale of my GoPro in Autodesk Fusion 360, once I had a that I created a box on the X & Y axis at the bottom of the GoPro model that was 2.5mm wider and longer than the GoPro, once that was done I extruded down the Z axis 2.5mm to create a base and extruded up the Z axis 15.00mm to create what would become the walls. On the outer edges I made a 4mm Chamfer and then on toe top I created a Shell Cut to creat walls 2.00mm thick (allowing for 5mm between the GoPro and the cradle, this should create a snug fit). Then I just cut out holes in the walls for anything I wanted to access such as the front power/mode button and the screen on the back.
Last step, I just created and extruded the little mount pieces on the bottom of the cradle!
(This is probably not a very good explanation but I wanted to put something here in case people wanted to try and create something themselves)