No need to really complicate this too much.... you will get good performance from the engine/aircraft combo, but we are not talking QM40 velocity here.

1) do not modify Jim Martin's design ..... !!! (blasphome!) Leave the ailerons as they are on the plans.

2) use HD aileron torque rods - 1/8" will be pleanty big enough. Goldberg use to sell a nice set of these I personally liked, but you can make your own. Key is in their installation - you want a tight bearing setup... no slop in the bearing, and the rod will not mechanically have slop in it. (review the torque rod installation for some of the QM40 and Q-500 aircraft.... I think DaveN has a link somewhere to a few posts).

My old Curare, Compensator, EU-1A and a few others all had s torque rod driven - single servo aileron installations. The EU1-A had some BIG ailerons. These were far-from-slow aircraft. Not an issue, but you must follow #3.

Yes the banshee has barn-door ailerons, but the span is not unreasonable. I saw quite a few of these aircraft fly, and all were build exactly as Jim designed the plane. Follow the plans. If you are concerned, using 5/32 tubing for the torque rods works nicely too. I would stick with what is on the plans.

3) SEAL the aileron gaps. That prevents your primary cause for flutter (differential air pressure bleeding through the hinge gap). Even a tight gap is not good enough. Must be sealed.

Bob