RE: using rudder
Yes, 15% is a good start.
But, also, keep-in-mind, that precision aerobatic planes do not experience as much roll-yaw coupling or adverse-yaw characteristics.
So, be prepared to break your own bad habits, when you fly F3A,NSRCA,or IMAC ships. Also,be able to define askid vs. slip in the turns.
Happy flying.