What is the total weight of the plane? I test flew one for a friend in the club that weighed 18lbs and flew with a saito 180. It had enough power but all the weight was glued into the cowl. Real bad idea, the cowl kept breaking off the mounts. With a saito 120 it should be under 14lbs at the very most. It lands pretty hot without flaps. I dont know where the cg is right off the top of my head but I can tell you that every AT-6 I've seen balanced measured from the forward section of the wheel wells. Make absolute sure what the correct way is cause it wont last long if its tail heavy. Use a real light touch on the elevator, you dont need a lot of throw. Otherwise it will snap if too much is used in a loop and go into a spin. Be up real high when you try that, it takes a little bit to stop the spin. Like most warbirds you want a fair amount of rudder and I dont really know how to tell you how much aileron. I call it an average amount, some have said its not enough. Best to setup with expo and dual rates until you get a feel for its character. My takeoffs were pretty smooth, the landings were like a ton of bricks looking for a place to drop. Keep on the throttle cause it stalled abruptly. Not fun at all. Would have been better if he had built it with flaps. I normally use around 100psi in my airtanks. I've been known to go as high as 120, but no higher than that. 80psi will work, I just like to have 4 or 5 cycles just in case.
Edwin