RE: Brian Taylor 81
Richard,
Don't know how much this will help, but here is my experience with the 60SP. When I purchased my first RCV engine, a 120SP for a very heavy TF Corsair, mboland eased my mind. He was correct in that the SP series of engines have an extreme amount of "pull". Large loops are not a problem.
I was so happy with that engine that I bought a 60SP for a .50 size Zero. The Zero weighs in at 7 lbs.-8 oz. and I'm turning a 15.5x13 APC bobbed to 14" dia. for ground clearance purposes. The 60SP turns this prop at 4200rpm with the big needle set a few clicks rich of max. rpm. On takeoff it takes about half a circuit to get up to speed, where I then throttle back to half throttle. Half throttle is where I run the engine, throttling up for loops or any manuver requiring a gain in altitude. I added flaps to the little Zeke to slow it down for landings as it's tough to slow it down with that big prop, even at idle. Add flaps. It sure helps!
Another thing, these engines are pretty stingy with fuel, which is nice.
Good luck,
Joe