John, take a look at the NSRCA website for the pattern guys. There is a good trimming guide that applies to all aircraft. I beleive the url is

http://www.nsrca.org/technical/trimm...mmingChart.pdf

It might be thrust. Fly straght and level at full power and kill the motor. See what happens. Could also be balance/incidence. The trimming guide should be able to help you narrow down your problem.

Howard