Scott is absolutely correct. I had been in the shop thinking about your issue and it occurred to me that a slight twist in one or more of the control surfaces could also cause a trim imbalance.
Two things to try. Line up the surfaces on both wings and pull a string from the inboard flap end and extend it out to the outboard edge of the wing tip. This should show any twists in a surface. Check both wings at the same time so that you can compare side to side.
Another option is to clamp a long piece of angle to the surfaces and see if everything is lined up. It would not take much of a twist in an aileron to make a difference in flight.
Tom Martin RV1 pilot 4.6hours!
CPL & IFR rated
EVO F1 Rocket 1000 hours,
2010 SARL Rocket 100 race, average
speed of 238.6 knots/274.6mph
RV4, RV7, RV10, two HRIIs and five F1 Rockets
RV14 Tail dragger
St.Thomas, Ontario Canada, CYQS