RC, I would estimate rpm somewhere around 9800 - 10,000 rpm with that prop.

I would put my money on the YS .63 being a little more powerful than the Saito .82 but to get that power advantage, I'd recommend letting the YS rev to between 11,000 and 11,500, static. They seem to prefer being in that higher range. With that in mind, try a 13x6, 13x5 or maybe a 12x8 and 12x7 as well.

Do let us know what figures you get. You'll love the engine - they are a real jewel.