RE: YS 63 best prop for pattern?
I once did a little more digging over in the YS forum and it appears the 63 likes to turn around 11,000rpm. When I went to the 13X6 APC I got 10,600 on 30% CoolPower.
I would think the 12X8 is going to load the engine too much on 15%.
What rpm's are you seeing with your current set?