Your question about the optimum lie for putters has been selected and answered on the podcast (click here to listen).
Your question about center-shafted and heel-shafted putters is answered in this recent Flatstick post.
I regard the "left-hand-low" grip form as fine, except for the "low" part. to make this hand "low" requires making the right hand "high" and this pokes the right elbow out, and this makes the right side more dominant and attention-grabbing than it should be. I just hand the right arm and hand as naturally as the left and put the right hand on the grip after the left hand gets there first, playing a support-only role. This keeps the shoulders level and neutralizes botgh sides for a relaxed, symmetrical setup and motion .
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