RE: Phoenix Sukhoi SU-31 Engine choice
I know you said you wanted to go with a 2 stroke, but you really should consider a 4 stroke. The 4 banger will swing a bigger prop=better vertical. Bigger prop=better breaking on down lines and landing. Just a thought.
I have an OS 70II on mine with an APC 13x6, and I am quite happy with it. She grooves real nice, and landing just requires that you fly er in. If I were doing it again...the Saito 82 would be the ticket. Go for the bigger bore regardless if you go 2 or 4 stroke. Mine is heavy, but you wouldn't know it, that's how well it grooves. Stick with the recommended throws. Too much elevator=snap/stall.
Have fun!
Jim C