This all brings up the discussion of fuel consumption in any model. In my opinion the best way to figure on this is to actually measure it while flying the model. Take for example the Tony's Bobcat..... He knows he has X number of ounces on board, and he sees the factory published fuel consumption. PLanning with that information he sets his flight timer to 5 minutes, hee lands taxis back and checks remaining fuel. He is not even into the hopper yet. He knows the hopper is 20 oz so he adds 30 seconds to his timer for the next flight. When he lands he has used about 2 oz out of the hopper so he knows he can increase his flight time by another 30 seconds and still be safe, and have enough fuel for a go around. The full throttle tests that Lee suggests could also give you a good starting point for fuel capacity sizing.