When drooping the rotor in a 3 foot hover even to the point that it touches down does nothing but show that the aircraft will settle to the ground from rapidly decreasing rotor effeciency because of the loss in lift associated with the slowing rotor RRPM like in a hovering auto. The rotor does not stall in that scenario. in order to create a full unrecoverable stall you would need a high up flow velocity through the disk like in a high descent and a decreasing rotor RRPM. The up flow can an primarilly does increase the AOA on the blades untill it reaches a stall . Pulling on the collective makes this happen faster only because critical angle of attack is reached sooner. The large angles of attack remain even at flat pitch and create huge amounts of drag wich you can not over power with the engine. Forget about the auto the rotor meets the up flow at a time when RRPM is below normal and the driving autorotation part of the disk has already been aerodynamicly destroyed . So there is no way to demostrate this due to that fact that it is fatal when encountered.