A couple of years ago I kit bashed a 54" wingspan, 3 channel Ace Air Scout trainer into a semi scale piper PA-12 Cub Cruiser. I added strip ailerons and used separate HS-81 servos for each aileron. They work well. I have added ailerons to several 3 channel planes when I built them and always used separate servos as for me it was easier than creating the linkage needed for a single center servo setup. My Air Scout/Piper PA-12 is powered with a .40 2 stroke and flys faster than a stock one with the recommended .25 and still no problem with the HS-81 servos.