Hi Anthony,
'First pull at the top' is designed to initially reduce excessive twist.
By having the bitter end at the top batten, (the first pull will be on the boom and lower panels), then the top batten will be the last part of the sail to react to trim, as friction in the previous blocks will have robbed most of the power by the time the pull reaches the bitter end. However given time and bouncing over a few waves, the friction will have shaken through the blocks and will have equalised loads.
PJR P. 68 Last para states:
"Although it might appear from the above that there is nothing to choose between first-pull-at-the-top and first-pull-at-the-bottom, the former somehow seems right to the western mind and all our recommended sheet systems are so arranged".
Have you considered a "split sheet system" as per PJR page 71 , to be able to separately control the upper and lower panels and so get optimum trim for the current conditions of wind sheer?
Yes, more sheets to pull, but you can do one at a time and with less load per sheet; and still able to cast both off at the same time if needing to spill suddenly.
Cheers
Ash