Best Cuben Fiber Pack – 40-50L

I am still working on getting pack weight down, but I put 29#'s in a Zpack Arc Blast and it felt like a 20# pack in my old Osprey. This pack is at the top end of your scale, but I easily put 7 days of food in it. The other nice thing is you can add the hip belt pockets and upper mest pockets and add/remove depending on what you need.

How much do you eat?
For 2 liters of water, they could go on your shoulder straps to keep the pack weight down if necessary.
Mind you none of the below is from experience, I'm shopping myself.
If you figure 2 pounds of food a day, you'd be just over 29 pounds for a heavy trip. Zpack claims to hold 30, Zimmerbuilt claims 35. Hmg claims over 50 for their 4400.
Zpack uses .78 cuben and coated .78 cuben. Zimmer uses 1.14 cuben, the same as HMG uses on their tent floors. To add strength, Zimmer suggests Xpac for the bottoms and sides. HMG offers a ripstop hybrid cuben. They claim over 50 pounds for the 4400, due to a plastic framesheet. The 3400 would be under 50. The 2400, IDK.
I'm kind of being torn towards the larger HMGs due to the versatility. For your size loads, I'd look to Zimmerbuilt. Zpack appears to be for those who are a little more hardcore with a lower base weight. I do see a lot of reports, like the last poster, of them being maxed out with no complaints. Actually it sounds like they all can be pushed a little on the rare occasion. It depends on how closely you really want to dial it in.

The HMG packs double up on the cuben fabric on the bottom of the pack, FWIW.

I only have experience with the HMG packs and the Porter will carry 35 lbs without issue. Assuming the pack fits.

I've got the HMG Porter 4400, which I use for winter trips or whenever I need the capacity. It carriesloads very well, and seems quite well built. No complaints.