Even though I portage boulders and logs for fun, I do have some experience with cuben fiber. No, the stuff ain't cheap.  I have made several air mattress inflator bags from it and did a post on that here on the site a couple years back with pics.  I got my material from ripstopbytheroll.com and completed the bags with the double sided 3M tape ST refers to.  (Jimbo, you might have seen it on the trip this fall.)  It's made with a single yard and the volume is the better part of 100L and packs down to the size of a deck of cards and weighs 1.6 oz with the nozzle adapters.  It is seriously strong stuff - they use it for world cup sailboat sails - that said, I did manage to tear a small hole in my bag two weekends ago on a backpacking trip.  It patched up real quick with a piece of cuben fiber repair tape.  Also, Big Agnes' most recent design backpacking tents they call Crazylight -   (You need to Login or Register uses that fabric. 

All that said, I think I'd still go with a CCS sil-nylon tarp as that stuff, while crazy light and crazy strong, is not crazy durable.  Just look at the BA site notes - " These products are intended for only the most advanced user. Although extremely strong for their weight, these tents are not indestructible and require careful use to decrease the possibility of damage. Special care during setup and extended trips is important as rough handling, long-term abrasion, exposure to sharp objects or rocky campsite selection may result in fabric punctures and tears." Whadya expect from stuff made from old milk jugs and pop bottles?

Hope that helps Jimbo.

And to Mossback's note, I'm partial to drams over grams as well!   :D

pd