The problem I see is that the default setting for EPA on computer radios is 100%. His servos should be seeing full travel as it is. I believe the 6EXA will allow EPA to be set to 120%, but I'm not sure any of this will fix the problem.
Do you have one aileron servo, two on a Y harness, or two seperate?
Have you tried flipping the dual rate switch? It may be that the factory setting for low rates is 50% or something. If so, simply flipping the Aileron dual rate switch on the TX may solve the problem.
(Cruz, many non-computer radios today have dual rates for Ailerons and elevator too.)
Dennis-