More nitro and more rpm also means more heat. That's usually not a problem, but if you're running a cowled engine that is not well cooled to begin with, more nitro can make things worse. Obviously not a problem with the orgional poster's setup though.

The extra RPM means more strokes per unit of time, which means faster piston/liner wear, but it also means more heat in the conrod, bearings, etc. So you get more wear in those areas. The extra (and IMHO, better) oil in the PM fuel over the Byrons will help, but it's anyones guess as to weither it will help more than the increased heat and RPM will hurt.

If it was me, I'd do what you are thinking of doing, going to a bigger prop to move more air with that extra RPM. If you like your level flight speed now, consider going up an inch in diameter rather than in pitch.