Ive had 2 of those, flew em both and sold em both...Im trying to remember. I had 3421s and 3301s but I cant remember which one went on the rudder and which one was on the ailerons. I want to say they were the 3421s though. In any case...be careful with the rudders on this plane. Both of mine were really sensitive to the rudder and had some roll coupling associated with it.