ORIGINAL: MTK

RG, FWIW,

With a little more stretched set-up we used to run 12x11, 12x12, 13x9 and as large as13x10 (around 10K) back in the day, on this engine and it's rear exhaust cousin. No pumps.

Ground clearance was built in of course and if yours just doesn't have enough, you don't have much choice but to use the smaller props..... Fuel milage really got so much better at lower rpm, many of us were using 12 oz tanks.

I heard of technique to determine how good the pipe setting for the load being turned was, in flight, and it works fairly well not just on 60's but 160's also: From a safe altitude and at full throttle, put the model in a shallow dive to unload the prop. If it goes rich and blubbers, pipe is long. If no change, pipe length is just right. If it picks up rpm and sounds lean, pipe is short