I have yet to toss a clutch due to an IRK, and my auto 70 spun to 14k RPM.

I have exploded a cast manual clutch before, but that was on a 107 motor with a normal flywheel and e-start, so it actually had a heavier flywheel setup than a normal 50. It didn't see much for revs (built to be a torquer) but it did see a lot of clutch dumps, feathering, etc, and was trying to haul a 270lb guy around on pavement. I'm convinced it's more the rider than the flywheel that causes them to let go. If you're smooooth... they hold up, if you're a goober, it's a goner.