I'm not a pilot, I'm a maintainer on a 412. After the first flight during a rotor track and balance procedure( if I may call it that), we set the auto-rotation speed to maintain 100% Nr or so. Yes, GW at the time of the auto will affect your Nr. I don't beleive a well maintained, well set up rotor is going to go past the dynamic parameters. Tha being said, when things go worng, they do go wrong, those damn swiss cheese holes!! I have seen close to 109% Nr though. HUMS shows a lot more than the naked eye!