I'm in the market for a pack that will hold about 4000ci. I have one of the original Osprey Aether 60s which is a great pack, but would like to get the weight down even further. I tried a GoLite Trek but concluded that I want an internal frame. I don't use a closed cell foam pad so can't use that to provide stiffness.

Anyone have any suggestions or am I already down to about the lightest weight I can reach for this type of pack?

I'd look at McHale packs. I've got 2, one monster and this spring I got a 0-Sarc UL. Not the cheapest, but you get the features you want, it fits great and hauls weight when you need to. I was curious about ULA, but I felt the quality, tailored fit, and service of Mchale was worth it.

Gossamer Gear Mariposa. Around 4000 cu. in. if you include the web pockets, two delrin stays, uses your sleeping pad as a framesheet, packs up really well, weighs 17.3 oz. I can carry 30-35 lbs. fairly comfortably with mine, although less than 30 is better. I'd avoid it for off-trail use, though as it is made primarily out of silnylon. They're also making a similar model out of ripstop now, but it's a bit heavier and narrower.

Well, I don't have a ULA pack (yet), but I've emailed Brain Frankle a few times about packs and pack fit, and I can certainly recommend the company from a customer service perspective. Check out the Circuit- it's a little smaller than 4000 cu.in., but it may fit your needs pretty well. Plus, from the looks of it, quality is top notch, although I don't have personal experience.

Our group of 10 just finished 12 days at Philmont, over 75 miles, lots of vertical, and two of us with new ULA Catalyst packs. We were both pretty happy with them. There are several changes we both agreed would help, and we're working on a review for that.

You may also want to look at the 3 lb Coleman external pack frame. How they got it so light is a mystery to me. It's bigger than the Catalyst, cost much less, has a lot of places for attach points, weighs a few ounces less than my Catalyst, and rode very well on one of our trekers.

MikeB

Another option would be the Six Moon Designs Starlite. It's 28oz with aluminum stays, also integrates inflatable or closed cell pads into the frame.
-Mark