Another alternative (better?) is the run the 4mm sheet from top down, instead of bottom up.
Scenario: wind picks up, you pull the 4mm sheet to flatten all battens/panels. Wind dies down a little; release the 4mm sheet a little, and the bottom panels gets camber first, while the top panels remain flat. Once the winds dies to light winds, release the 4mm sheet completely.
Certainly, experimentation is needed; maybe releasing the 4mm line a little, causes all the battens to equalize, and all the panels are midway flat. I suppose, one can put different strength bungees according to top or middle or bottom battens.
Doing it this way, there is little weight of the 4mm line from the boom to your cleat point. You don't need as long as a line, and you don't have a long line from the top batten to somewhere at your deck.
Whereas, original way, if you run the 4mm line to the top most batten, that ~10m (mast height dependent) of 4mm weight is "adding" to the friction (of the top batten block) you are trying to counteract.