Homer said that you can't swing faster than you turn.
What about someone like Kenny Perry who is a long hitter, yet his hips and shoulders are approximately square (parallel to the target-line) at impact? He has great compression, so is he a counterexample?
P.S. the photo I was looking at was from around 2000.
Matt
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"In my experience, if you stay with the essentials you WILL build a repeatable swing undoubtedly. If you can master the Imperatives you have a champion" (Vikram).
The reason you can't sustain the lag is because you are so eager to make the club move fast (a reaction to the intent of "hitting it far"). So on a full shot you throw it away too early, which doesn't happen for your short chip. (bts)