Gomer (and others)
I have yet to see anyone who has had a real, unannounced engine failure from 100' not have damage to the helicopter and their body. There's a good reason for avoiding that area.
(I've probably done close to 100 demonstrations of the HV curve to budding test pilots and flight test engineers, as well as participated in a few real world HV curve demonstrations for certification, just to establish my bona-fides).
If you've convinced yourself through lots of training for autorotations that you can do a zero airspeed entry from 100' and got away with it, you're deluding yourself that when the real, unannounced failure happens that you can survive - the important part you're not thinking about is the surprise, it can't happen to me, this isn't true part of the real engine failure that deprives you of the very important two to three seconds that the training aspect doesn't consider. You're ready for the engine failure, know what's going to happen and are spring loaded to react to the first twitch of the throttle from the instructor.
and for those of you who think that you can get away with it from a 20' hover, much the same applies.
Everyone I've talked to who's had a real engine failure has said the same thing- the surprise factor caught them big time.
And just to round this out - when doing a zero airspeed entry from a high hover in a Jet Ranger (one of the more forgiving machines to do this in), it takes a minimum of 250-300 feet for the airspeed to start approaching something that will let you flare and have the rotor start to get back into the green. This is with a one second delay between rolling the throttle off and lowering the collective - a very short time.