RE: O.S. VS. SAITO???
I've owned both Saito 4-strokes and OS 4-strokes & 2-strokes. The Saitos are a good engine but the OS's are superior in my opinion. The OS 4-strokes tune easier, make great power and don't spit nearly as much oil all over the airplane. I know a lot of Saito enthusiasts will point out that the they are lighter, etc. but I think an ounce or two is a small price to pay for the ease of use and performance. The OS 1.10-FSa is absolutely outstanding. It makes tons of power, idles like a Swiss watch, starts easy, tunes easy and there is almost nothing on the airplane at the end of the day. I also just ran an .81-FSa tonight. Same thing. Fired right up, tuned effortlessly, will idle all day, no goo on the airplane and it seems to be making more power than my Saito .81 with the same prop before it is even broken in. The OS FSa 4-strokes are pricey but they are really, really good.
Unless OS really takes a negative turn, I will never pay for another Saito.
So you won't necessarily go wrong whatever you choose but I'd go with OS.