The trailing edge shape of control surfaces can have a large effect on trim. One check would be to make sure that the aileron trailing edges have not been damaged or deformed during storage. Also that the covering is in good condition and is not pulling and distorting the trailing edge.
If the aircraft feels one-wing low, it is important to determine whether it is a control trim problem (force is required to keep the wings level but no stick movement) or a wing rigging problem (the controls need to be deflected one way to keep the wings level).
Just a thought.
KZ8