After reading all the "flutter" threads, and being the proud owner of a NEW ARC (uncovered) DP Extra, I had a great chance to take a look at all the suggested trouble areas. A couple of things seemed obvious, so I built them in....I'll have photos later.

Basically, I installed additional ribs in all the aileron bays at angles from the LE of one aileron rib, to the TE of the adjacent one. On adjacent bays, I reversed where they started from, so there are ribs going in both 45 angles from LE to TE (hard to picture, I know). Anyway - twisting the uncovered ailerons by hand seemed to reflect that these ribs made it a lot more rigid. And added .1 oz per aileron.

In the wing, it seemed the ply plate that the aileron servo bolts to in the wing had a lot of flex, so I put a 1/8" x 1/4" spruce longeron on edge from the spar to the trailing edge, gluing it to the ply plate in the wing. THAT made the ply plate MUCH stronger, and I doubt they'll oscillate under load now.