Factory Jetting is not for the engine,but for EPA regs. Motor has not changed, jetting has.
I've wondered if the counter balance might not be just right for the piston and rod. If I was going in far enough to crack the case, I'd wanna start there. If anything had to lose weight to balance ,,great..
If you can get the flywheel and not go all the way in,then I'd first check its balance, then mass, then consider how to and how much to lighten. A percentage of mass ,, gotta be some kinda guidelines out there..
Www.lightenmyflywheelnow.please