I use a Pizzaz with an OS 70 Surpass II for 3D. I've tried a YS 45, OS 40SF, OS 46 FX on a Sig SE and I got real tired of hearing the racket these 2-strokes make. I much prefer to hear the 4-stroke, and now that I'm doing TR's closer and closer to myself and to the ground, I REALLY don't want to hear the noise from a 2-stroke. The OS is 3 ounces heavier than the Saito, but it is much quieter too. The power band has a nice torquey sweet spot at mid-throttle too. It seems that when I move the throttle I don't even hear the engine rpm's vary, but the plane does jump up. I think the .53 two-strokes would probably be ok with the 12.25 x 3.75 prop for hovering power, but the sound of a 4-stroke is so nice, especially when I'm the only one at the field. I had a TT Extra with a 46FX on it, what a POS that plane was. It's heavy as a brick. The fuse weighs 12 oz alone, and the covering was not even as strong as shelf paper.
I used a 14x4 prop on the OS 70, but have settled on a 13x4 3D prop. It spools up a little bit faster than the 14x4 and runs a bit smoother at top end.