Oddly enough I found shooting at 12" length prone more stable. So I ordered a S25 as well.

I hold the buttstock underside with my left hand to stabilize it and of course at 12" it is too high so my left hand cannot rest on the ground. What I do I also use a backpack and put it under my left hand so the buttstock of the rifle is over my left hand which is over the backpack.

I've found this setup to be incredibly stable.

I'm going to leave each attached to a rifle; I'm taking two hunting with me - a Cooper 280AI and a Win 70 30-06.