I'm on my second Cermark; using four 60 oz-in servos in wings, wyed upper servos into ail channel, lower two into aux channel, one elevator servo (90 oz-in) is working out fine. Run 4.8v 1000Mah JR extra pack. Weighs 10#-6 oz with supercharged YS 1.20 and I have not been out-performed by another Pitts. I had a GP 1/3 Pitts that had good power with a Moki 2.10 and my Cermark flies better. Have seen no need for aileron differential...JIM