I alternate between two packs: the GG Crown 60 and the ULA Catalyst. I use the Crown 60 for shorter trips and the Catalyst for longer, due to its greater weight capacity.

The Crown fits fine up to a little over 30 pounds, then it sags and pulls on my shoulders annoyingly (perhaps what you're experiencing). I've reduced this somewhat with the new accessory air frame, which is also super-comfy on the back.

The Catalyst is almost perfect, except for a shoulder strap that turns inward and bruises my chest if I'm not careful. It can support a week-long trip and is pretty much all the pack I need for bigger loads.

ULA has vast fit options, so I''d bet you can get one to work quite well. They're certainly tough and well-made.

Cheers,