I used my 6900 Sky Talus on a sheep hunt and ended up packing out 12 miles @ 83# to get to our extraction point. Throughout the packout I tried different tensions between the shoulder straps and the belt, but my back was definitely hurting no matter how I had it, and I had trouble keeping it up on my hips, but it was my only backpack hunt so far, so I don't know if the issue was me not knowing what I am doing, not having much of a rear to keep it on, or what. Maybe all packouts are like that.