Here Joe:
You might have an issue with the gas tank located so low. I had played with modifications years ago and found that the air from the muffler was not sufficient to pressurize the tank with it so low and the added tubing.
I had rebuilt the thing in college and on first run on the big field at school, some bump in the ground I think caused some flex in the engine mounts and the prop hit the throttle cable and rudder cable. Throttle cable wound itself around the engine and the plastic rudder tube/cable was sliced and diced.