I own a GP .60 size Extra. It has a Saito .91 turning a 14x6 prop. Great power for me, and it will hover and pull out just barely. I would not put anything smaller on it no doubt. My tank fits perfect and is exactly where it should be, I've never had problems with the engine or tank placment.

Most 4 strokes sound the same for the most part, especially Saito and OS. Someone with enough experience can tell the difference, but it's not a huge one at that.