Yes, I was wondering whether you’d looked at rafts and cradles etc. I believe they did that at Easter Island, but could you make one that was strong enough? I would have thought the ancient people would have had something of that nature because so many megaliths are such awkward shapes.

Maybe the most robust and lightest arrangement would be to lash the sarsen to a couple of longitudinal logs that would be lifted along underneath the stone, so the shape of the stone became irrelevant? (You’d need a raised “track” comprising occasional transverse logs, so there was room to put the levers underneath.) Something like that would be good because you’d have lengthened the whole contraption so there’d be room for more rowers and the weight would be evenly distributed – no-one would have a heavy bit compared with the others, and everyone would be doing the same rowing action at the same height. Also, distributing the weight along a greater length would improve the steering and enable you to tip the front up more easily when you needed to.

PS have just tried it in the garden with an almost round rock, and it seems to work small-scale…. I’m glad people think you’re mad. My neighbours now KNOW I am!