Pka,

I have the same engine as you w/ pump. My extra is set up stock. For the longest time my plane did weird things when looping, especially when coming out of a loop. Extra would drop right wing. Had an expert buddy fly my plane and he said there was really nothing wrong with it except it does some unexpected moves during a loop. He tried both inside and outside loop. Same result. He suggested since my cylinder head is on one side that perhaps its not balanced side to side. Sure enough when he picked it up it tilted towards the cylinder. I ended up placing bunch of weights on the tip of the wing (opposite of the cylinder head). Walla, plane now tracks much better in all orientation.

Jimmy