I’m not sure about the lateral force either, though I have the same feeling as you. I’m not really sure I understand why there’s a lateral force at all, but I suppose there must be one, since your pallets moved back. Maybe there was some slippage along the pivot point, and that can cause it? Yes, that’s probably it, if the stone pivots perfectly then lateral force may not be a severe issue but if the stone is slipping down the pivot point at the same time then the whole stone is actually moving downwards and since it’s presenting an angled face to the pivot point it converts the downward movement into a sideways force. Or something. C’mon Steve…!

For the purposes of experimental modelling, what are your thoughts on the height of the pivot point for a 32 ft stone and an 8 ft hole? As low as practicable obviously, but how do you see the trajectory of the stone? Presumably, you’ll want it to smack into the near side of the hole at the end of it’s arc? (Or do you?) But near the top or near the bottom?

That word “smack” would be a very satisfying conclusion to the stone tipping. We don’t want to stop all those pivoting tons suddenly, only to watch an unpredictable and uncontrollable bouncing effect. One thought would be an elongated hole, like a trench, with the nearside in the form of a “stopping bed” at an angle a few degrees off vertical and pointing directly at the pivot point. Perhaps with an earthen mound or timbers above, forming an extension to this steep angled surface? Ok, you’d end up with the stone slightly leaning, but it might be worth it for the assurance of a “clean stop”. (Always assuming you think we could then easily haul it upright of course. Could we?)