May I suggest having a look at the Elemental Horizons line?
I took a custom made Aquilo on the Larapinta trail, and was very happy with it. My starting total pack weight was 18kg (39.6lb), and it went up, with two days worth of water, to about 21kg (46lb). It carried the weight comfortably.
My medium has a volume of 3587 cubic inches, according to the website, but the X large goes up to 4723 cubic inches.
Quality of workmanship on the pack is good, with great attention to detail.
Matthew is very open to doing custom work, he used Dyneema in specific areas on my pack, and it stood up to the rough country just fine. He was quick to respond to emails, and even upgraded the postage to international express at no charge to me, to make sure I got my pack on time.
Total weight of the pack, with custom fabric, and pockets, is 1054g (37.2oz) on my scales. I paid $303, in March last year, for the pack with 2 x accessory pockets and hydration sleeve.
Will Rietveld gave the Aquilo a Highly Recommended rating when he reviewed it.