You should have at least 80% of the entire weight on the iliac crest of your hips. There is no significant weight on your shoulders if done properly. I put the pack on my back (shoulder straps super loose), sliding it up so the hipbelt centerline is slightly ABOVE top of the iliac crest of each hip, then tighten the heck out of the hip belt. As I stand up, the ENTIRE pack weight is resting on my hips - the shoulders straps are not even touching my shoulders. I then snug the shoulder straps down to just resting on the shoulders (probably only 2-3 lbs of force on each shoulder). Then tighten the sternum strap and other load stabilizer straps. Don't feel bad, I didn't know the proper way to wear a pack for my first 50+ years..............it was a complete game changer. Short story is there is very little spinal load if the pack fits you properly and you wear it properly.