I actually meant to post this shortly after the article was published. As an MYOG junkie with a fetish for streamlined packs, I rushed to follow Jay's directions as quickly as I could! In true OCD fashion, I made not one, but TWO of these nifty packs on consecutive nights, one slightly smaller than Jay's model (for those insulation-free South Texas nights), and one at the recommended size, but with two larger side pockets - I found the one in the article a bit snug for my preferred bottles when the pack was fully loaded. The first one took me about 5 hours, the second one about 3.
In response to the previous poster - I haven't had any trouble with the seams on my packs, but to this seamster it sounds like the fabric itself tore, which just means you exceeded the strength of the VERY light fabric that was used. Lots of guys have had lots of luck with spinnaker and cuben, but my personal preference is to have a pack made of slightly sturdier fabric - even standard 1.4 oz silnylon - just so I don't have to fret about my gear. The design is solid, so give it another stab with a more durable material!
Another idea would be to take the top stitch that Jay uses to reinforce the seam where the shoulder strap tops join the pack bag AND where the front panel joins the bottom, and do this down each side seam. This would increase the strength dramatically.
Here are some pictures for your edification:
:Pack 1, back view
:Pack 1, side view - you can see here that the backpanel is just the same silnylon that I used for the rest of the body. The shoulder strap lower attachments and the facing parts of the shoulder straps themselves are made of uncoated 1.9 oz ripstop nylon. The failure of this pack was that I used the 5/8 inch grosgrain I had lying around instead of the 3/4 inch, which would have matched my ladder locks. This slipped - a LOT. It's an easy fix, and the pack is a nice size.
:Pack 2, back view
:Pack 2, side view
:Pack 2, front view - for this pack, I made the backpanel/bottom out of Dyneema gridstop - about 4 oz/yd2. It's not light, but it's a fabric that I don't have to worry about if I dump my pack on our local blend of cactus and acid-etched limestone, or take the occasional booty-scoot on a particularly nasty bushwhack. I also substituted some of the grosgrain for actual webbing - however, the proper size grosgrain worked just as well and is lighter.
:Pack 2, worn - notice the full 1L Platypus in each pocket. The "failed experiment" with this pack was trying to use spectra line for the pocket drawcords. Not only do I miss the elastic bungee, but the microscopic cord locks from thru-hiker.com don't grip the slick cord very well.
Jay's article was fantastic - I really didn't have any trouble following along, and his suggestions were just the ticket when it came to modifying the pack to fit my needs.