Four strokes are Awesome! I like the crisp, sharp, powerful transition from idle to full throttle. I don't get that with my two strokes. I also like the way they spool down faster. Generally, you can run a larger prop on a four stroke, and it doesn't sound like a flying weed eater.

As for upgrading--the saito .56 is not a powerful motor. I mean, it's powerful for it's size, but it WILL NOT win any pylon races. It would be right at home on a little 4.5 lb 3d plane spinning a 13 X 4 prop. For the decathalon, I'd go with the saito .72. Much more power, and the same sized case. When you take the .56 out, the .72 will mount right in without re-drilling anything, and is overall about the same size and weight. A little heavier and taller, but not much. Mounting dimensions are about the same! Talk about waking a plane up!!!