Hi A and C,
Perhaps a more symbolic solution would be some white and red paint applied to the offended area. The white in the shape of an "H", and the red, a circle with a diagonal bar bisecting it. Not an ICAO recognized aerodrome symbol I'm sure, but it'll get the idea across!
It will be a lot less effort than the confrontation with a pilot, or figuring out how to chain a rotor without damaging it!
Best of luck, Pilot DAR