You know how it goes, kind of hard landing, re-gas , take off and the motor doesn't run right. Now you're 30 seconds into a combat round and you realize your clunk is forward. Try this, take out the fuel feed inside the tank, cut the line at the halfway point and pit a 2'' to 3'' piece of brass tubing in the middle of the line. Leave some loose fuel line at either end so the clunk moves around but the line can't go too far forward because of the brass stiffener. I did it to my SPA3D yesterday and my combat planes are next.