CG Ultimate 2-stoke advice
I also have a Saito 120 and agree that it's a perfect match. If you have to go two stroke, I think a strong .90, 1.08 or 1.20 would do well. I have the Webra 1.20 in a Sukhoi and like it a lot. Be aware that the Ultimate cowling is not huge and that some engines may require careful planning with regards to exhaust routing.
Be careful about weight.