The OEM Pipe on my Ultra Flash kept flattening the centering tabs at the rear end of the pipe. The end result is the outlet moves about 1/4" up and down from center. I don't know if the movement was connected to several stalls that inexplicably occurred at half speed or not. But this winter I took the pipe out and repositioned the tabs so the inner pipe is much more stable. I would think the pipe would have been self centering on the straights and vectoring a bit with Elev and Rudd.

At our Jet Rallies, I have seen one pipe "squirt almost entirely out the back and one come out only a few inches. Both planes landed O.K. If I recall correctly, the one with the squirted pipe had some fire damage though. I have since come to the conclusion that a loose pipe = no flight.