Personally, I think that a 70 size 4 stroke engine will not be big enough for good flight. The Saito 82 is what I'd call minimum size. It flys it good, but certainly doesn't have too much horsepower, and that's with 30% glow fuel. No way a 70 size eingine would do a decent flat spin, let alone a rising flat spin which the UCDs are famous for.

I'd use a bigger engine.

thanks
Barry