I have an OS 40SF in RC configuration with little run time on it, looks new. I am the original owner. This is the ball-bearing, rather hefty engine that as I understand it is the side-exhuast sibling of the 40VF. Mine is the ringed version. A flying buddy has one, the ABC version, converted to CL use in a Pathfinder that it pulls very well. Question: Is the 40SF a good stunt engine if fitted with venturi and CL NVA, based on anyone's experience out there? I would expect a high-RPM, flat prop, straight 2-cycle run like the modern crop of high-revving engines. Further, would the ABC piston-liner be preferred to the ringed piston-liner?