It was just another thought. There's no reason why the pole has to go down to the bottom of the hole. It ought to make contact with the monolith at a point that will end up being just above ground level when erected. It may be necessary to bind the pole to the monolith to stop it slipping (a socket timber lashed to the stone would be good), but these forces are quite small compared to the compressive load on the pole and the tension in the rope. My idea was that this system would raise the stone all the way from 70 to 90 degrees and would bring it to a nice controlled stop automatically. A rope with the weight at the middle might not do this in one go, although I haven't worked out the numbers yet, so I can't be sure.