Agree with crab...
There was a low-rotor rpm demonstration that was shown to me at the Robinson factory years ago, which I would also demonstrate to students, (this was back in the day before the governor and when we were still required to demonstrate Low G).
In a hover, slowly roll off the throttle and try to maintain a stable hover over the ground. Depending upon weight, I have had the RPM at 78% and recovered--with throttle.
Please do not try this in flight---Perform the demonstration at about 3 foot hover, and it is more to demonstrate the effectiveness of the tail rotor, I doubt you could recover the RPM in an auto-rotation--although I could be wrong.