No, I don't know anything about helicopter aerodynamics except from what I learned in my PPL (H) training and have gathered around the net - that's why I'm asking all these (apparently) stupid questions. Never did allude or pretend to be eductaed in the same either - I just like to educate myself and am naturally curious.
Now that we know I'm an uneducated fool and that's out of the way, let's get back to business and leave haughtiness behind.
"Reducing RPM in flight"
If you were to reduce RRPM in a, say, H269 just for the hell of it, it will of course stall at some point. But not immeditaley at lower red line - there must be an area of lesser performance before it stalls, no? Also, if I recall correctly from my aurorotation days, one had to keep a vigilant eye on the RPM so as not to over-rev the rotor on the H269. Therefore, if you were to reduce RPM to just when it stalls, can not the RPM be regained by a combination of/or autorotation and throttling up again?
"We had thought they were expensive because of all those pesky machined parts that are flight critical, so we were working on that, but now we find that if we just gave the parts valium everything would be easier"
Of course, but there is a reason that Robinson de-rated his Lycoming engine so it would last longer. No engine likes to run at top RPM for long periods. That's why Rotaxes don't last. The H269 is apparently quite known for having a highly strung engine that fails quite a lot, which I myself experienced.
I will definitely look into reading Prouty and other aerodynamic books, but forums like these are invaluable for empirical data.