I know this is backpacking LIGHT and all.... But I feel like there's too much emphasis on weight being the be all end all.... I'm super happy that my pack is much lighter now (around 11-12# before food and water), but at that point I stop carrying about exactly how many grams/ounces I'm carrying since it's so comfortable as it is. Plus, better leg workout with more weight, right, folks who skip leg days??
Anyways, I think it's really cool you're making a new fabric, and more importantly, like your other products, it'll be made in the USA, I assume, so that alone makes it worth it. I've never really had a problem with sagging tent fabric, but that's because I use a short length of shock cord at my vestibule tie outs, which is the only area that really has any potential to sag on my double rainbow.
With as light a pack as I carry now, I'm happy to focus my attention on comfort and convenience. Plus, cuben is prohibitively expensive for me.