If money is no issue then go for the Saito 82, you will not regret it. Its better than an OS70. I had a Funtana too and flew is with a Saito 72, its enough for hard sport flying but not really for hard 3D. Trust me the Saito is user friendly. As long as you are patient almost all engines are user friendly.

Stay clear of the Saito 91 as I think the crankcase if larger and you will need to work on the Funtana's engine mounting. Stay with the 70/72/82 ...