RE: U-Can-Do Saito 100 or OS 91fx?
Tri:
I have not flown the Ucan Do, but on engine size, for the power, go with the 91FX. The Saito 100 has less power in that range, you would need a 125 at least and then a shy short of power. IMO I woulduse the 91FX. You are trying to decide on what engine to use. Find the aircraft's manual, and it will state what engine is correct for this model. Use the power formula, for 2 stroke cc"s multiply by 1.5 toget a 4 stroke equivilent, that should help on your decision.