FH1100, just to clarify,
Tip plane path = a flat disc traced in the air by the spinning rotor blade tips.
I'm sure you know that.
It is nearer the ground at idle RPM because the blades droop. It is therefore more likely to lop your nut off. Also cyclic control is not effective as the blades are not flying.
unless there is no gravity in Pensacola
edit: It occured to me that if you fly a jet powered thingy (FH1100 perhaps)the idle speed may be significantly higher than a piston Enstrom. I dont know about jets and I did qualify it by saying it may be different for other types.
An Enstrom at idle with the clutch disengaged will be doing about 40-60 RRPM depending on how it is set up. Not enough to lift the blades off the stops but enough to give you a fair headache.