Hello; The only Kadet ARF at our field has an OS 52 Surpass in it. I have flown it almost every weekend since July when it first showed up, and the 52 works pretty good in it. The owner just did his first landing last weekend. We fly at sea level here, and the Kadet isn';t a speedster no matter what engine you put into it. The other one I see a few times a year has an ancient Enya 60 four stroke in it, it probably makes less power then the Surpass 52. As far as Saito's go, I think anything from the 50 up to the 72 would please you. I saw one with a Saito 80 in it years ago, but the guy sold me that engine and put a two stroke in it. We have a bunch of LT40's at our field, mostly two strokes but there is one with a new Saito 40 in it, it works pretty hard to keep that plane up, I think a 50 or 56 would a lot better.