1. Don't try to use the elevator to correct a roll problem. Besides putting a twisting stress on the fuselage, the roll correction (if any) will change with both airspeed AND elevator input. Ick!

2. The floats may be contributing to this, but the first place I'd look is the wing. It's probably got a warp in it. Assuming it's covered with a heat-shrink material such as MonoKote, you can heat the covering while holding it straight (maybe overcorrect slightly). Repeat until the ailerons trim flush with the TE.

3. Lateral balance may also be contributing, but I'd eyeball the wing for warps before adding wingtip weight. Rx for lateral balance is to compare inside loops with outside loops (assuming the airplane is capable of outside loops). If it rolls the same direction both inside and outside, lateral balance is not a factor; the problem is purely wing twist. OTOH, if it rolls left on an inside loop and right in an outside loop, the left wing is heavier than the right. Or it could be a mix of wing twist and lateral balance. Work slowly over many flights and you'll eventually get it dialed in.

Duane Gall
RCPRO