Lightened flywheels affect rev speed, not rev limit. A lightened flywheel will reduce the amount of rotational inertia of the engine, but that only affects standing start take-offs when the clutch is engaged, not top-end power. Any time you run an engine harder than it was designed you increase the wear and tear, there's no avoiding it. Just because your instructor is a mechanic doesn't mean he knows what he's talking about. I've built enough engines in various power output trims to confidently stand behind what I say, and it sounds like he doesn't fully understand what a lightened flywheel is all about.