How should I prop my conversion engine? A friend of mine runs BME's exclusively and he recommends proping at about 6500RPM on the ground.

I just don't have any experience with gassers. This is my first one and I'm about ready to fly this plane for the first time. It's a MW Extra 300S.

I've got a Poulan 54cc conversion here. Running on Ralph Cunningham ignition with full synchro-spark. Timing at 28BTDC. Fuel is pump 87octane with Husky oil at 40:1 mix. Bisson muffler from a Moki 1.80-exhaust header on muffler enlarged to allow for clean flow and the ends of the tubes have been cut off about 1/4". Muffler is fairly quiet.

I'm getting right at 6950--7000RPM with a Pro Zinger 22-8 prop. 6000' above sea level and low humidity. Temp in the high 70's. Occasionally my tach will read about 7200RPM- but 6900-7000 is an average reading.

Should I try a 22-10 or a different prop in the 22-8 size? I'm hesitant to spend $200 on a bunch of props, just to try them all out.

Also, I can't unzip that thrust calculator that you can find on the internet. What kind of thrust am I making with my current prop?

Thanks