Age is catching up on me I'm afraid. I think I went for an apc 11x8~11x9. The japanese were going for higher pitches like 11x10 because it was the era where everyone was sensitive to noise pollution,but I never had any success probably because i was running 10%nitro.
These engines were designed for 10~20% nitro. It was known as the PA104 pump system and they recommended mounting the pump such that the pump centerline is level with the carb inlet.
The diaphragm pump wasn't very hardy though and occasionally tuning the engine could be a problem.Hope this helps.