Ok, here's the situation: I have Goldberg 10-300 Ultimate Bipe 60" WS weighs about 11lbs with a Zenoah G20ei turning a 16x6 Scimitar prop. It flys great, rolls are crisp and will knife-edge with almost 0 coupling. But....its snaps out at the top of a loop. I am baffled. CG is right on, maybe just a tab noseheavy. Could it be too much elevator?