I think it is important to understand why certain things work and do not work for someone. This topic isnt about subjective preference/style. Lets get objective.
Afaik, most backpacks like ULA have a flat back. Now compare this to aarn and Roger's pack design.
Why have a frame?
The frame holds the blueprint of your back shape. Our frames are easy to remove and custom bend to match your shape, creating the blueprint. The frame’s job is to maintain this shape when the pack is loaded and to bring the load as close to your back as possible.
Why other packs are a backache waiting to happen
Frameless packs, and the most common internal frame system, twin vertical stays, give the worst possible shape for back comfort. When these packs are stuffed tightly, the backpanel rounds out to a convex shape horizontally (A)—the opposite shape to your back. The side profile is increased so that the load is positioned further from your back, and the load is concentrated down the spine. The the pull back pressure on the shoulders is increased resulting in a greater forward lean and increased back strain! The addition of a plastic framesheet is an improvement as it keeps the backpanel flat horizontally (B), bringing the load closer to the back.
Why our packs are backsavers
We take pack design further with the concave backpanel (C)—a custom mouldable shape- that brings the load closest to your back. The vertical divider further narrows the profile (D). The result is the most upright posture and the least back strain. Even with Balance Pockets, it remains important to keep the load close to your back, because the smaller volume in the front Balance Pockets cannot fully counterbalance a pack that hangs far from your back.
Having tall, narrow bottom, wide top, high CoG is not enough. I think it is important to have a backpanel that matches your back shape.
More surface area of contact=better load transfer to the back.
>I use them to spread the weight and stop jarring impacts, particularly coming down hill. In places like Nepal I would use them even if I wasn't carrying a pack.
Have you noticed sherpas carry heavy loads WITHOUT any poles? Have you also noticed that they dont wear hi-tech shoes?
Pls read the links I posted.