I remember reading a Clarence Lee test of the YS 60 SE around 1980. He called it the strongest 60 he had tested at that time.
I promptly got one and it has been a jewel of an engine that is no more finnicky about plugs, fuel, props, or pipes than other glow engines. This is still my favorite engine of any type, with the 45 a close second.
My only YS 4 stroke is an FZ 110, and while it certainly prefers higher nitro, I have used 15% as well. I just love YS power.
For me, the pressurized fuel system is a major positive. YS engines have been used by so many competition fliers over the years and it is not because they are too much trouble.
Capt. Sluggo