Check out any older Dana Design Pack. You can easily find them on Ebay for a decent price. No need to spend big bucks on a pack that's gonna be abused. They are indestructible and carry weight better than any pack I have ever used.

My friends and I used them to haul camping gear, a week's worth of food and climbing equipment into the mountains. I only ditched the pack because I swore I would never carry that much weight ever again. Fortunately climbing gear has shed as much weight as backpacking gear.

Good luck in the search.

Edited by rOg_w on 02/19/2013 20:24:56 MST.

Thanks everyone, I've got plenty of leads to look into now.

Anything from Mystery Ranch will suit. MR is owned by Dana Gleason, whose original Dana Design packs are praised above. Expensive though, and many old Dana Design packs can be found on eBay. I've used my ULA Catalyst for five years now without ripping the mesh (despite plenty of bushwhacking). The pack (about 5000 ci, XL frame) handled 45-50 pounds without much trouble. And this past summer I tested a BD Mercury 75 and thought it was great at weight transfer and management. The Mercury comes in smaller sizes if you don't need 7500 cubic inches.