May I make a suggestion?
-Take the camera and hold it in your right hand. Take something else similar (like a balsa block) in size and weight and hold it in our left hand. Do the balance test with your hands and see if they are similar in weight.
-Take the similar weighted item and the camera to the post office and have them both weighed. Explain what you are doing, and go early in the morning when they are not busy yet. (they do look at you strange)
Once you have all that, you can strap it to the bottom and see if the thing WILL FLY before smashing both your plane and the camera
S