feihu

Before you do anything, here are some things that you might consider.
Are you using a 3 channel radio or a 4 channel radio?
If you're using a 3 channel single stick radio, then you can't revert back to rudder only in flight; you would have to land and change plugs in the receiver.
If you have a 4 channel radio, then you can fly with either rudder only, or ailerons only, or both.
Regarding the modification you would have to make, I think the simplist would be to mount the aileron servo on top of the wing and use strip ailerons with tape hinged to the trailing edge of the wing. You might build a base for the aileron servo so that it can be taped to the wing so you don't cut into the wing, but I think that cutting a small rectangular hole in the top of the wing might anchor the servo sufficiently.
Now, depending on the dihedral of the wing, ( which I expect might be 5 - 7 degrees) the aileron effectiveness in flight will be compromised. So there can be a condition where full aileron with dihedral results in a steady state bank. For maximum aileron effectiveness, you need ZERO dihedral.
Now you can either make a dihedral mod to your AeroCruiser or build a new wing with zero or 1-2 degrees dihedral and have excellent aileron control, but then you will not be able to fly rudder only for turns.
Another consideration is how the added weight of the aileron system (servo and ailerons and control arms hookup) might affect the flying.

Or you might consider a new airplane with ailerons.

feihu