Rick said: John,
Thanks for the actual experience, that's great! I'm curious how it actually takes substantially longer, just getting everything fastened in? Hell, if you could get it dialed in you could pack into the bag without disassembling.
I wonder if time was saved throughout the day not rooting around the pack (this can be minimized but sometimes you want that sweater you didn't think to keep handy)
A lot of things already get stuffed into a sack. So that time is a wash, the fastening those sacks (or pouring them into a packbag) is the variable. I think that's where the key lies anyway, it's easy to overdo that and make a frame/harness/strap system that is heavier than one with just an actual bag!
The issue is the attachment method that I've gone with for ~90% of my gear. Items I need during the day (lunch and afternoon snacks excepted; I pull both of those at lunch time) are located in easy-to-access points (I have a mil surplus MOLLE sustainment pouch on my left hip and a mil surplus water bottle holder with a pocket on it on my right hip; my poncho and any possibles clothing go on some shock cord I've woven through the top three PALS array rows on the back panel). However, if I need something from in a sack (like my lunch), I have to loosen the straps holding the sack to the back panel. This takes a bit of time to do, but more to reverse, as the weight distribution needs to be correct and the straps have to be tight to prevent slippage (and possible loss of gear!).
The morning pack routine goes like this: pull the pack and ditty bag off of the hammock suspension, grab my food bag from the nearby tree, detach my poncho from the hammock (if I'm using it as my undercover), skin the hammock and insulation, roll up and skin the tarp, and detach everything from the trees. Now I've got a pile of gear. If I was using a single-bag solution, it'd be simplicity itself to just stuff everything in there (done it). However, I've got my DIY pack, which requires a bit more work. My skinned hammock and tarp go on the bottom of the back panel; this requires threading my tree straps through two PALS columns, then placing the hammock on the panel, tightening the center strap (which isn't a tree strap, but I've found helpful in stabilizing the load), placing the tarp on top of the hammock, and tightening the tree straps at the outside left and right. Then I need to place my food bag on the panel and tighten those straps down. Then I need to place my ditty bag and poncho on the panel and tighten those straps down (though, if it looks like rain, the poncho goes under the shock cord at the top of the panel for easy access). Then any clothing that I feel I might need during the day goes under the shock cord at the top of the panel.
It sounds easy, but fiddling with slippery silnylon sacks and polyester strapping when you're half-awake Before Coffee is more difficult than it sounds. So, it takes me ~15 to 20 minutes more than it would with a single-bag solution. YMMV there, though.
Also, I agree that you're going to gain pack weight with a modular system. The majority of a pack's weight isn't in the fabric that it's made out of; at most, you're looking at ~1 square yard of fabric. The difference between 30d sil and 1,000d CORDURA is going to be ~9.4 oz at that amount. The real killers on pack weight are all of the accoutrements associated with it: the foam in the waist belt and shoulder straps, the extra webbing for attachment points, heavier buckles, a frame, zippers, closure methods, etc., etc., etc. So, the attachments that you're looking at for this one might add a significant fraction of the total pack's weight, when it comes on down to it.
If that's worth it to you, then go for it! I'm pretty happy with my pack for heavier/bulkier loads, but I've finally gotten my 3-season gear down to where a week will fit in a ~40L pack with no real concerns, and my base weight is under 9 lbs before the pack. So, I can now design a pack around the idea of one big pocket for the majority of my stuff and a couple of smaller attachment points for immediate-need items. It'll save me time and hassle on-trail, which is really important to me on longer days--I'm not a particularly fast hiker, so efficiency trumps everything else.