You can balance the main rotor blades to bring them into trim (or use the trim tabs -depending on your type of helicopter) -but how on earth are you going to adjust autorotative r-rpm?
We are NOT talking about adjusting the normal r-rpm during flight...just about the free-wheeling r-rpm....
Why should one go into the "high-risk-area" of massive overspeeding, when he needs to pitch the r-rpm down afterwards?
I agree if you say-keep the r-rpm in the high green limit.....so you have more power to cushion the landing..
But i disagree (in my own personal opinion and experience) if one is continueing telling to keep the r-rpm highly over the limit...