Clarification on the 'laces down' foot thing would be needed. Upright doesn't do it because it doesn't define the a plane of reference... not only that but even not laces down, most people's feet aren't vertical, or sometimes straight (bent toes etc).
The hands thing could be problematic in that I can touch my trigger hand against my left leg by extending my fingers and still take a shot. I don't. But I can. With ease. And it helps.
But I'm not sure how to rule that out. You could say the trigger hand can only touch the rifle I suppose.
And obviously, if you're bag is under you're knee, you don't have 3 points of contact with the ground...
Fun aint it?