Tim,
Check and recheck your elevators to make sure they are dead even. I had mine slightly off from each other the first few flights which induced a little aileron trim and thus a roll when the speed was different (slower or faster). One twist on the clevis corrected it all - no roll now.

I did try pushing the nose weight way up to the front to see what trim changes I could induce - It really had very little effect on the flight characteristics.

Too bad I missed the D2 contest!

Joe