I use lock ons and on the 2 support bars, I weld a cross piece of 3/8ths bar steel and drill a 3/4" hole. I then put a 10" lag bolt into the tree with a 1/2" drive ratchet. I then put a motorcycle cable around the stand and tree called a Kong Cable. None of my stands are under 20 feet. I know all the work I go through putting it up and if they are willing to go through that much to take it down, then have at it. If they want it, they will have it, just not easily. I hunt private property.
I did find 2 years ago someone was using them while I was gone. I just took the floor and folded it up and locked it with a cable to the frame.