I had a very similar situation last year on our lease. One guy put 2 stands out. 1 was very similar to your situation, except he didn't use a contraption. He placed his stand actually overhanging a creek that is the property line, facing our land which was covered up in buck sign. The other was 100 yards on to our property. I moved the one stand to face back in his direction, and confiscated the other which was well on our property. I also put up posted signs at each one. He removed the one facing our property by the same afternoon of the morning I posted it and confiscated his stand. Another stand was at a property line juncture and my son was hunting with his back to the other property, and a guy walked in on him from the other land, and refused to back out, although my son was there first and was not facing his land. His stand also was overlooking trails on our property which do not cross over to his, and he was very upset when I told him that we would continue to hunt our land. His justification was that he had hunted it for years--it didn't matter to him that he was trespassing each time that he shot a deer there. I had another instance of poaching on the other land I hunt near my home. essentially my whole season was affected adversely by this type of mindset. The good news was that I got 2 arrested on the land near my home--but not until well after the damage was done.

There is a fat, lazy, no good pile that hunts next to a friend of mines land, and he uses an old van, and he has it about 20 yards from the property line. My friend has permission to hunt the same land the other guy hunts, but it isn't any good because they are loud, and have the deer scared off around there, so it sucks.
On another piece of land I hunt, thereare some people that live next to it, and they trespass all the time. My uncle caught them on it once, but I see tracks and sign from them being there, and we have found dead deer and turkeys on the land, and the blood trails from some were fresh enough I tracked them back to behind their house. It really sucks.