I posted on the other question about the SK engines. Only ones I have used are the .91s and I like them better then OS but have only been using them for just over a year now. They tune just as well as any OS I have ever had. Most of my two strokes are OS though or have been over the years, you can't go wrong with one, well, I never have anyway. Your SK is also a ringed engine with a tapered bore and designed with different timing and transfer ports for lower RPM and more torque. The .91 will run lean with any prop on it smaller then a 15X6 but I have tried a 15X4 and had no problem. They only run up to about 11,000 to 11,500 RPM so they are not good for any type of racing. Knowing this you should be happy with the SK. In the small two stroke engines my #1 is the OS .55 AX, after that I go to the SK, I also like the TT pro series. I don't care for the super tigres or magnums at all but that's just a personal choice thing, a lot of folks love them. I run mostly four strokes these days in glow power and my #1 choice is YS then a tie for OS and Saito. I like pumps on my engines so OS usually wins out. For gassers I have a number of different engines but only one of each, I like the Zenoahs and the extra few grams of weight have no meaning to me. I really like the SKs!!!