I would try more downhaul as a 'first easy fix' to see if I was able to get both leeward and windward telltales to stream properly when the leech telltales break 50% of the time. If you get better speed and pointing that way, I would start changing my mast setup to make it match the luff curve.
If the sail was made for you, the sailmaker can probably help you with some figures to get you into the ballpark for spreader rake and tension. E/P sails are good guys from what I know about them.


I never liked the tension meters/gauges. I always measure spreader rake by releasing tension before putting a batten from tip to tip on the spreaders. Measure distance to the luff track. Then tension the spreader wires and tie off the halyard to the boom. Measure the distance from the (now tied on tight) halyard to the mast track at the spreaders. This is your spreader rake and pre-bend when done the old fashioned way.

The way you described on hoisting the main outside the track and comparing curves is good. The real proof is when you go sailing though.

The flatter sail will get you better airflow over the sail and more leech tension. It should result in better pointing and speed. Please keep us posted and study those telltales. They tell us all we need to know to get the setup right, but it takes some brainwork



I am not certain if I understand the question. What you just wrote above is the ideal trim for max power for least drag.
What you wrote earlier was that the top windward telltale lifted and the leech telltales stalled (separation in front of the leech). The latter description sounds like there is too much draft in the sail for the windspeed. Perhaps I can answer more fully if you try rephrasing your question.