I had a similar problem, ultimately solved by getting a Granite Gear Nimbus Ozone, as the straps can be adjusted wider or narrower, and up and down the frame as needed. You can have the manufacturer swap belt/straps as you like as well.

Unfortunate, the "ultralight" versions of mainline packs seem to lack the features that make packs fit people.
"In the beginner's mind there are many possibilities. In the expert's mind there are few." Shunryu Suzuki