I'm glad to hear that things went well for you. 3.5" if the furthest forward that I've heard anyone balance a H9 Corsair. You might try moving the C.G. aft 1/8" at a time to see if you like the flying characteristics better or worse. The Topflight .60 size Corsair is also comparable to the H9 Corsair and the Top Flite is balanced at 4.25"
http://www3.towerhobbies.com/cgi-bin...&I=LXHU80&P=ML The large prop that you are turning may have some unique aerodynamic effects that require a more forward C.G. than most.