[drewitgolf]

I can't really envision getting to Follow Thru before Impact. How does that work? Is that a throw away, no lag etc?

All that an a whole lot more. While the definition of Follow-through (8-11) is the section that covers the interval between ball seperation and position of Both Arms straight, all too often on the lesson tee I see students get to both Arms straight before Impact. These Storage Issues can be the result of over-acceleration by the Pivot or independently of the Arms, or a Pivot that stops because to the intention to hit at the ball.
No matter how hard these golfers try to get their Hands into a good Impact Hand Location, they just can't do it...until the instructor informs and explains.