[Mike O]

What if you got a different . . . hiccup . . . grip type? What's vertical then?

Maybe nothing then. That's why in post #11 I said 'assuming you take the grip with the left wrist vertical.

Homer's point in 10-2-G is that if you don't have some visual geometric validation for any particular feel- then as he says "Feel loses it geometric basis" and that's why he mentions the "True" Swing in 10-2-G because those grips are theoretically speaking only ideal if one were a "True" Swinger whereby centrifugal force automatically aligns the clubface- in relation to the body i.e. how far back or up it is in relation to the pivot. As opposed to a Ball related "manipulated swinger" where by while you are still using centrifugal force for accelerating the shaft- but you over-ride the automated alignment of the clubface based on the line of pull through the longitudinal center of gravity and you just make sure that you come into impact with the left wrist in its correct alignment- whatever that is that you may have pre-chosen.

It's like two layers of using Centrifugal force- the first layer is for the clubshaft and if you just completely let it control everything then the second layer is for the clubface.