I ran a 12X6 on my GWS can motors, and they burned up fast. I think running the smaller prop is what's keeping your amps down and not burning your motor up. The 11X 4.7 ought to give quite a bit more thrust, but it's gonna draw more amps and your motor will be hotter.

Bad thing is... I was running an 11X6 (12X6 cut down) and I though it was doing pretty good, then went back to the 12X6 and holy cow!! It kicks major booty. The difference was pretty noticable.