I have a flywheel made, most likely from 6061-XX. The original machining tapered the crank mating face a few thousandths, as if to perform as a belleville washer. After a partial season that section is badley fretted at the face OD, and riddled with lightning bolt cracks commonly associated with stress corrosion cracking SCC. Some of the various 6061 alloys have fairly poor ratings as resistant to SCC. Also 6000 alloys are forbidden in some MIL spex to be part of structural weldment on shipboard. I picture 100 kmiles zooming along a US rustbelt roadway as a more corrosive atmosphere than a few outings in a race car's bellhousing, so would hesitate to use 6061 in a stressed state, like with fitted taper bolts, press fitted bushings, etc.