Print with supports on build plate at 0.2mm. Increase infill density and/or perimeter count and/or material used to suit your strength needs. When you try to insert the ¼" screw, you'll need to penetrate the one-layer thick “threading” before screwing it in to attach the camera.

So I saw this video:

Unfortunately, the OP wasn't sharing or sell the 3D model, so I had to model it myself from scratch. 

With the power of the few GoPro mounts and the Insta360 X3 I had, as well as a dollar store ruler and some guesswork, I think I have modelled it to perform relatively the same function but with a few of my own improvements.

1. The inner walls are bevelled inwards to fit the curve of the Insta360 better, allowing both surfaces to contact each other more
2. The additional thin layer should make it harder for the ¼" screw to come out

As usual, it's modelled crudely, so remixes to simplify the process in Fusion360 would be greatly appreciated.

And yes, I've tested and it works with the X3 and One X2

Link for 3D printed GoPro Harness. It works really well, highly recommend if you have the time to get the correct materials.