Sail structure has changed dramatically lately with the availability of HM carbon for both rigs and sails. Doyle Sails was the first of the large sailmaking groups to figure out that sail structures have been built back-to-front for the past 50 years and decided to do something about it. Now their structured luff technology is leading edge in dynamic response. Having the most stable and lowest stretch fibre paths and strength in the front rather than the back means that the luff area remains stable along with the built-in shape there. With the luff area remaining stable, the leech becomes more dynamic and can flatten and twist under increasing load. If we look at any wing structure in nature from birds to insects, they also have the same structure. You'd think sail designers would have paid more attention to this over the past 20 years when the science was there to allow us to see how wings on these creatures of nature manage to fly in the most remarkable ways with barely any effort.Mate, I'm not a sailmaker, but I know what I want.
I have watched Maka, on countless occasions, possibly the WING, C-Rigs and the C2Byte rig where the most challenging, because they were free standing, but even the XX and 29erC rigs, the boat would be on it's side, we weren't getting what we wanted, so addition of a bit of Carbon tape here or there altered the whole dynamics of the sail and it's response.
He would then go away and re do the top of the sail by altering the rocking of the panels to achieve the same response.
As it has been explained to be, it's about keeping the elongation of the Mylar within it's elastic limits (the Carbon tubes are no were near their Elastic limits) so it can react many many millions of cycles the same way. In any given race any sail many react 200-300 times per windward leg, so to ratchet up 100,000 is not that hard. In a year you will hit 1m easily.
Again, as mentioned before, back in the 1990's, we measured the fall off of very hi end alloy in 3-4 months of sailing 18teen 4 times per week (with 3 rigs) so in-effect if you had one rig sailing once a week you would expect some alteration (may not all be bad) in 3-4 months.
If you are going to hang a spinnaker of the top of a mast, then the strength and the rigging of that mast is such that you can't mast the tip flexible enough to make a Pin (ellipse) head work properly and if your sailing a single-hander, and if you want "sparkling" performance down-hill then the extra area up hi, working well up-wind, that will kick in down-wind and make it so much more enticing.
So your right, but you need such small movements in the Mylar to achieve great gains.
Chris Carin's did it with Dacron, Norths are now doing it with 3Di just a different order.