Chris--yep, the pad sleeve has some shockcord sewn into the top but opens just underneath the straps:
to occupy a tri fold torso cut "blue pad" (I reinforced the fold seams with foil duct tape)
Mark, you're absolutely right about Rockywoods sometimes unhelpful product descriptions. The backpanel and pad meshes are their "dry-tech knit mesh" backed with an uncoated (very breathable) 160 denier ripstop Cordura.
Here are some pictures to better show how those layers went together:
I sewed the mesh to the uncoated Cordura, turning them effectively into a breathable, mesh-against-skin, but still weight-bearing appropriate layer--which I then sewed (the permimeters) to the XPAC. After which, I turned that inside out (right side out, actually) and inserted the ventilated foam cutouts.
And as for weight, I still need to find and add the removable sternum strap adjusters I want, but that's a matter of grams, so the basically complete pack (with compression system and shockcord, but without 7 oz torso pad) is ~23 oz.
That's just a cheapo kitchen scale, but it rings up a hair over 24 oz with two Cokes on it, so I think it's about right.
And, I must confess, I had lots of help/lessons from an extremely accomplished seamstress (my mom), so every time I thought I broke the sewing machine trying to bartack through two layers of ripstop nylon, webbing and a strap of seatbelt, she'd come to my rescue.
Also, I just re-read my first post and realized I said "Granite Gear" when I meant Gossamer Gear.
Thanks to everyone for the compliments! I'm taking the pack out the week after next for a field test, I'll report back with shortcomings as I find them.
Already I know it's probably bigger than I need (though I'm really proud of my compression system that can be used without interfering with the pocket contents, so it'll probably be always partially cranked in), and if I could (had to?) do it all again, I'd cut the front panel in a very slight trapezoid (13" wide at point where it connects with the bottom, tapering to 11.5 or 11 inches wide at the collar), to keep the weight even lower/closer.
Finally, I'm thinking about adding a removable curved stay. Anyone have any ideas? If I got a pair of aluminum arrow shafts, could I bend them into a slight S (enough to keep the bottom of the pack against my lumbar, and bring the top closer to the top of my shoulderblades) without weakening it too much?
Here's a shot of how it carries:
And Joe, I'd love to, but I Silk Street-ed enough other packs that I think I'd owe way too much in intellectual property royalties/patent infringement to sell these things.