Don, I don't think it is quite that simple, it'd be nice if it were. There are numerous other factors to take into account. Among them (but far from complete) would be:

Amount of cast off or on
Angle of the comb line
Thickness of the comb
Pitch
Shape and location of the hand (wrist)
MOI of the gun
Positioning of the rib

I don't think gun fitting has ever been reduced to a science but is considered to be more of an art though the "science" is a good starting point.

John McCain is my war hero.