You might want to check your tank. I was having a problem with mine, I was getting only about 1/2 the time in the air, and whenever I went to a nose high attitude the engine would sputter and stall (interestingly enough, in a simple, tight loop the engine was fine). I took the tank out of the plane and found that the hose the klunker is on came off the brass tube. When I'd go to a nose high attitude all the fuel would go the back of the tank, and the brass tube would be out of the fuel.....so.....no gas, no go.

Since I fixed the tank it's been working great.

Oh, and centrifugal force is created by objects spinning, what your thinking of is inertia (object at rest stays at rest, object in motion stays in motion). In a dive the fuel would tend to 'float' in the center of the tank.