I'm a bit confussed, isn't Pentex approved for J30 Mains, and aren't Pentex sails "String Sails" ?
If I've done this right, I am attaching a picture of a J-30 Sail made from Pentx that I am told is Class Legal.
West Marine Affiliate Program
The J/30 Class Association has partnered with West Marine and is now a member of the West Marine affiliate program. You can support the J/30 Class when you make your West Marine purchases online. The J/30 Class Association receives a percentage of sales from your purchases when you click through from our website. Click the logo above and you will be directed to the West Marine website with a cookie that identifies you as a J/30 affiliate. You can also use any discounts that you may be authorized.