Justa add 1" to rudder, I have the stock and it might need some more rudder, but the elevator is plenty enough but rudder could use more.

Also adding counterbalances is not worth the trouble as they are not huge surfaces and they are solid balsa.

If I would do againg I would put two aileron servos to the wings and forget the tarque rods. That would be all the mechanical changes.

It flies nice and fun plane. Put a nice .46BB engine and you will have plenty of power.