Hello; We have two of those here with OS 70 surpass', work great.
another fellow has an old Enya 60 4-stroke in one, with flaps, that works good too.
My personal choice would be the Saito 72, because I don't already have one, or maybe one of those RCV 58 sleeve valve engines. I'm sure a Saito 65 would do it too.
I hope you have lots fo fun with your plane, whatever engine you decide on.