Above, a collection of different cheap mounts, made from off the shelf parts from home depot.
On the camera end all decent cameras have a cavity that takes a 1/4" 20 thread count bolt. You want your camera to be pointing the right direction when the bolt is snug. So I use a wingnut on the end of a 1' bolt, that goes through a threaded schedule 40 1/2" endcap, secureed by a locknut. Obviously you need to drill a 1/4 hole in the endcap for that.
Then you just need an extension (PVC schedule 40) and the part that secures the mount to the frame.
A schedule 40 PVC 2"x2" T piece with a threaded 1/2" exit works great for the keel, leading edge or Xbar.
Or a 3/4" x 3/4" x 1/2" T for sprogs and downtubes.
Cut off a bit more than half.
I used a wire brush to take off the rough up the inside of the pipe (after it showed me some 'tude)
Also take off the sharp edges and bevel the corners (while you fill you hair with white PVC crumbs)
The "ruffed up" PVC will now let the glue stick to it, like a wuffo to a late to setup hang glider pilot.
Mouse mat neoprene works great and seems to last for ever. Well 4 years of Tandems and counting.
Shoe Goo works a treat for the bonding (don't sniffit - its not the good kind of glue)
There we go pretty easy stuff.
Sometimes you might want to get a bit more fancy with those angles. The GoPro has its own swivel system but only in 2 axis, sometimes you might be coming out of a zipper pocket (huh !?) or maybe just going for something new and you want it at a certain angle. This nice ball head mount can be the ticket ~$18. SLIK SBH 60
but if you are mounting from a sprog, say on a sport 2 all you need is this (and some zip ties) and a saftey would be smart too.
Maybe I should try to sell them... Anyone want me to make them one ?