Very nice model! I want to do that one someday. What kind of rubber do you use? Just the stuff in the kit? If so, that might be your problem. My models barely flew at all with the kit rubber, so I bought FAI Sport or Super Sport 1/8" rubber. You can get it on Ebay really cheap. I take a piece of rubber 1.5 times the length of the model, tie it and double it (fold it in half) and use that. Lubricate the rubber first with Armorall. The doubled rubber gives a lot more power and flight time. Even if your model is heavy, if you want to fly it 20 feet, give FAI a shot. It might work. I did the 900 series Mustang this way and also the Super Cub 95- both are terrific fliers. Have Fun!