A heavy wing (roll trim imbalance) can be caused by a lot of different things...
- Improper shape of aileron trailing edges
- asymmetry (difference) in the shape of the two ailerons
- One or both ailerons not mounted at the correct elevation in relation to the wing
- A weight imbalance in the airplane (One occupant sitting to one side, etc.)
In many cases it is probably a combination of all of these.
For this reason, zeroing in on one specific method of correction without checking all possibility is for the most part a band-aid fix... not fixing the actual problem (or at least not all of them) is not the proper way to deal with a trim problem.
Having said that, incorrect aileron shape is the most common cause and should be the first thing checked. it can have a strong impact on the handling qualities of the airplane also, so bypassing it because of a fear of reshaping the aileron is not a good idea.
Every RV that has folded trailing edges on its control surfaces should have their control surface shapes checked closely prior to first flight, as well as any airplane that it is not known whether they have ever been check (you are second owner, etc).
The process is detailed in Chapter 5.7 of the current rev. of Section 5 of the construction manual. You can access it
HERE