GoPro low-profile swivel mount

I wanted a swivel mount with as little projection from the surface as possible. The easiest way to get that is to build the ball right onto a clip mount. The usual M5 nut and a GoPro knob lock the mount in place.

The ball is 19mm diameter, which I gather is a common size, so it might be useful as a basis for other projects.

Edit 2016-08-06: sadly, the ball connection to the clip was a major weak point, and having to print with that orientation means it's not really feasible to strengthen i