Hi Airmaniac

Myself and Chevelle fly together at the same field. He is an engineer and his knowlege is beyond me by far in the tecnical side of it, but I have been running a magunm 61fs for over a yr in mine.

I have a Magnum/ ASP 61 in my Eindecker. Which is the bored out 52fs. Basiclly I have just a little more HP then you. I am runing a 12X7 groupner on mine using 15% Nitro and I'm getting 9800 RPM's. I could get up to 10 if I pushed it. I've run countless gallans of fuel through mine. I would say you are just a little over Proped and loading up the engine. If you are trying to fly scale I would go with a Groupner paddle style prop and drop to a 12X5 or 11X6 groupner, that is unless your looking for speed. It will give you tons of torque even at low RMPs. I fly mine really slow in a small box and can do some really great stuff with it close to the ground because I have the torque to pull out if I get into trouble.

The zinger prop is a good prop, but the Groupner paddle will gove you tons more pull with the same RPM's or even less RPM's. The groupner cost a little more, but on a four stroke they are worth it.

I guess really before the question can truly be answered we would have to know how and what you are looking to do with the plane.