While we wait to see if Arnaldo (writer of the article) answers my request to step in or send me his reply, I'd say that what sailmakers tell customers is naturally biased by their specific business needs (as anyone's, for that sake - no recriminations). More resistant materials mean less stretchy materials. But it also means less weight, less work (aligning panels' stronger direction with stress lines is time consuming) and more profit (higher cost materials + less work time + same profit % = more $$).

Add the fact that rigid sails ARE superior in racing conditions - when everyone is supposed to wear the sails that best suit the conditions most of the time - and the rigid sails sells themselves. And what would anyone atribute the performance to? The sailcloth, naturally.

But what he said in the article is that the story is not necessarily the same when you are cruising, when the pressure is very volatile, when the cost of aligning those panels is less important in the total cost of the sail and/or your rig is less high-tech then windsurfers (or some beach cats). Jibs, for example, are a lot more dependent on sailcloth flexibility and design exactly because they are not attached to a flexible/adjustable mast. Even more, if they have no battens.

Hopefully, both Dave Calvert and Arnaldo (author of the article) will go on with this thread. I can see that I'm just repeating the same reasoning... Sorry, this is already beyond the limits of my knowlege!