Tail Stinger Takeoff Prevention  

First, we have to suspend reality a bit to believe he is able to grab the tali stinger and assume the aircraft is already airborne because most stingers are going to be tough to grab when on the ground.

Second, it depends on the aircraft on what happens next. In general, the extra weight from a person hanging on will not over power the rotor or the engine. However, the fact that they would be hanging at the furthest point on the aircraft the moment would shift tremendously forcing the pilot to apply far more cyclic than normal. Some aircraft may react better than others to that. 

In reality, a pilot would probably not be able to respond to such an unexpected change. So the prospector miraculously graps the tail stinger without hitting the the tail rotor. Amazing. But then the aircraft crashes tail first onto him.