Like Charlie says, go to Vans Aircraft site and get the heavy wing document. It is a good one.
If it has flown balanced before the incident, that is a great help in diagnosing the situation.
Jumping forward, assuming it has flown in balance previously, and also assuming that the heavy wing is only due to this new aileron, then it is likely, one of these, or a combination.
a. TE radius is too small, or less than the original part.
b. There is a bow in the aileron, or less/different bow than the original
The bow difference could be as small as .020"
Possibly needing radius adjustment and/or hinge height adjustment.
Lots to check in that document first, though.
1st Flight 1-27-18
Phase II 8-3-18