Hello; Have you considered Saito? The Saito 91 is much lighter then the OS91. The Saito 100 is lighter then the OS 91.

I would use a Saito 80 in place of a 60 two-stroke, but I'm sure the new Saito 82 would be just as good, just lighter.

A consideration is the power to weight ratio, modern Saito's weigh less then the two strokes of an equivalent output. Lighter flies better.

I have an OS91, but I have never used it, no that's not completely true; I put it in a GB Extra 300 then I put it in a GB Ultimate for a little while before I bought a Saito 91 to put in there. Good engine just heavier then it needs to be.