I have a new Tenzing 6000 and have been getting in shape for this fall. I hike with a 60lb bag of salt in the pack but have been getting a lot of pain between my shoulders and the back of my neck from too much weight pulling back on my shoulders. Is it because i have too much weight in the pack? (about 75lbs total) or because its not distributed right? I put my sleeping bag in the bottom and all my weight is at the top. I have a 31-32 waist and the hip straps are tightened the whole way and it still seems like not enough weight on my hips. Any solutions?