Have you carried a pack with no belt compared to a pack with a belt?
Having the weight on your spine compared to having it on your hips makes a considerable difference.
I tried-on a few different packs at a sporting goods store and was amazed at the difference in fit between brands. Some so bad that if that was all I had I'd carry my things in a duffle-bag, others fit like a glove. Arc'teryx backpacks >worst fit to my body type, Osprey for the win for me.
Good luck finding what you want.
