Totally agree tqmatch
Fly 7, this is almost the greyest of grey areas.
Carry a camera on board - no problem.
Rest it on the vacant seat next to you with it filming, don't think that would be a problem.
Rest it on the window frame, OK - however, it won't stay there but a bit of bluetac might sort it? No, OK I'll try a bit of double sided sticky tape. No, how about one of those GoPro sticky pads? A clamp etc. etc.
Hang on though - don't those GoPro 4 use Bluetooth and Wifi? Can I use those during all/any stages of flight - Ah, that is up to the operator - is he aware this is a portable electronic device?
Hence my original response - I tried to avoid the term 'risk assess' but in the end, it comes down to you trying to think what might happen if your stress/bonding analysis fails, your secondary restraint method fails and the outcome is bad.
Cheers
TeeS