I’m using the crudest of mounts – a piece of 3M Heavy Duty Fastener (e.g. Velcro) stuck to the frame under the battery. All my cameras have a matching piece of fastener on them. I’ve marked each cameras’ CG with a dot of silver marker pen.
One of my cameras has a wide-angle lens added on. The lens attaches with a magnet but I didn’t trust the magnet, so I’ve secured it more permanently with a little J B Weld.
See a test video using this setup below the photos.
mQX: heavy duty velcro mount under battery compartmentmQX: onboard HD camera w/wide-angle lens