Modding is fun, but nobody does it as well as the factory.
i could not DISagree more with this statement.
the factory bikes are not tuned to their max, not even close. i have balanced cranks from the Ducati engines and the difference is phenomenal. Ducati cranks are NOT balanced and lightened to the most ideal point, same with the pistons and rods.
the problem is cost: if the factory did that with every bike, it would raise the cost significantly, probably as much as 800-1000 to the retail price. so they statically balance to a good amount, test the engine to 10000 rpm (using an electric spinner, not running the engine) and if the thing doesnt' vibrate too much, it passes.
put the high comp pistons on, but make sure to get them balanced along with the rods. if you have the time and money, get the crank dynamically balanced and lightened. tune the system on a dyno with a PCIII and the stock EFI and you'll blow any s2r1k off the road.