For the Sunday Sailor:

Old boats can respond well to batten tuning simply because the common fiberglass battens get stiff with age, and therefore respond well to thinning thinner the thin way by sanding the forward third. Often they are too stiff and will not allow the sail to shape in light air off the wind which is disasterous. I prefer to try and duplicate the real thing by rigging the sail, mast, downhaul and boom on sawhorses (main sheet to mast base). Not perfect but better. Then pull a string from mast (rotated) to batten tip and measure and mark point of max draft with pencil. Fool with battens and batten tension and shift your points of maximum draft so they all fall proportionately along each batten or in a line from top to bottom of sail (dependent on your philosophy). If nothing else, this gives you a good insight into your sail, and an oportunity to examine it under different loadings. Someone else I spoke to rolls a pencil (marble) on sail with sail chords level to quickly find max draft point.

Mark batten with marksalot which is visible thru sail, to denote correct pocket insertion depth (at time of setup...) and max batten draft point for reference later on water

Hope this helps someone...

On the beach always lie on your back under boom and sight up rigged sail and get a feel for the mainsheet tension/bend/flatten/downhaul relationship. Worth a few hours on the water. Really.