1/4" is alot of aileron. This is not a simple lateral balance problem, or it's a huge one. My vote goes elsewhere.

First, check that the rudder is straight. Out of trim rudders will cause the plane to roll due to dihedral (roll coupling).

If the rudder is straight, check that the fuse was built straight. Simply sight along it, if it's out much, you'll see it. If the fuse isn't straight, it'll have the same effect as rudder trim. You can work around it by applying opposite rudder trim, if repairing the warp is too much work.

Next, set the plane up on a table or something in a slightly nose-up attitude (5 degrees or so). Stand in front of the plane, directly in line with the fuse. Walk backwards, watching the underside of the wing. If the underside of one wing becomes visible before the other, a wing is warped.

Determine which one, and if you've covered with a heat shrink covering, you can twist the wing in the desired direction, and heat the resulting wrinkles out of the covering. The covering will correct minor warps. More extreme warps will require that the wing be uncovered, glue joints broken and remade until the wing is straight.

For sport planes, I perfer to have both wingtips warped downwards about 1 degree. This is called washout, and will help ensure stalls are straight ahead. It comes at the cost of more abrupt inverted stalls.

Hope this helps.

J