I designed a mount for a GoPro camera to the picatinny rail of a NERF foam dart gun.
The NERF part is identical to my "NERF dual gun connector" connector and thus should fit perfectly.
I obviously coult not test how well the GoPro part fits.
It should be a very tight (0.1mm allowance) fit and follow the curve of the housing. So the camera will not shake loose and will always film straight ahead.
Both sides for the NERF rail and the GoPro M6 bolt are tapered to make insertion easier.
Update: perfect fit!
Update 2: improved version with trapped nut