i have both and was wondering which to build first. for higher hp, it is recommended to start with a genuine honda {or so the engine builders (agk, nr, gecker etc) say}. as far as i can tell, the 6.5 has a longer stroke; is it in the rod or piston?. any idea if these pistons can be turned down. the low comp (dished) ones. how many rpm are the stock honda fly's good for?