On some of the round track cars, we would routinely machine 1/8" or more off the clutch disc side of a small block Chevy V8 flywheel, then turn it around on the lathe and take a bunch off the engine side. That was done to lighten the rotating mass to allow the engine to accelerate quicker off the turns, and give faster compression braking at the end of the straightaway. I don't recall ever breaking one of those flywheels, even at 7K+ RPM.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!