RE: Camera Size For A Slow Stick??
Slow sticks are cheep to repair... I stuck mine 50' up in a tree and getting it down poked two holes in the wings and ripped the rudder and elevator off... Point being I repaired it in 15 minutes and was flying again.
Be adventurous, before you put the camera on, cut yourself a 2x4 piece that weight is similar to your camera, strap it on and try flying it. Remember to figure the weight of a 3rd servo to press the camera button.
Good luck, post us your results!