In reply to mlt: I have a big Arcteryx Altra pack but I wouldn't call it minimalist as such. It is very comfortable, but not a "tube with a harness and a lid" if that's what you are after. Try the big POD X-Pod if you want simple, but it won't be as comfy a ride as a big backpacking sack (which will weigh about a kilo more).
I bought it to replace a dearly loved 20+ yr old POD Expedition (ditto the 45kg carry at about 5500m), because now I am fat and have children so I want comfy slippers not alpine...
I also tried a Gregory Baltoro, a huge Osprey Zenith and a cavernous Macpac - I'm happy with the Altra but it does indeed squeak so I'm going to grease it up before the next outing.
Scandinavians, Kiwis and Canadians all worth looking at as well as the Yanks - some big trips to be done out there. I always quite fancied the Mystery Ranch stuff (I bought my wife a Dana Designs Bomb Pack many years ago and it is still insanely comfy, if heavy) but nowhere to try it on that I could find. Also better suited to carrying sniper rifles etc. Should you be in NZ try the Cactus Foray as well.
Good luck with your insane loads
Cheers
b