If I remember right it is measured from an imaginary line between thepivot points of the limbs to the backside of the grip. If this is true then what is considered the pivot point? The end of the limb inside the limb pocket, the limb bolt, the point at which the limb leaves the limb pocket? It seems to me that with pivoting limb pockets the pivot point would be the last one I mentioned.

Pivot point is that point where the limbs contact the rocker underneath the limb.