Was wondering what you guys think. I have several old pattern engines that put out substantial more power than todays 61 size engines. My dad and I ran one of our old OS 61 (rear exhaust long stroke) with fuel pump and tuned pipe 2 weeks ago and have decided to try it on a UCD. It turned a 12.5x11 APC at 11,000 rpms with instant throttle response. Does any one have any idea what size fun fly prop (14x4, 15x4) would be a good choice for tins engine. He has the OS Hanno Special that he is putting on his UCD now and it turns a 13x11 to 13x12 in the same rpm range. Also these engines have lots of torque with excellent trottle tansition. Do you quys think this will be a good combo?