I had some issues with finding packs that would fit me as well, but in the opposite way - everything was TOO big. I'm short and have a short torso. For me the packs that were adjustable from XS-S, S-M fit the best. Once I bought the pack, I loaded it up with my gear and then took it to REI and they helped me adjust it. Some packs/brands have the ability to switch out the belt or the straps. So if you are having issues with straps but not the belt, then you can look into getting a different size strap.

I'm pretty loyal to Gregory but I do have one Osprey bag - both brands have adjustable packs. I would look at Gregory Maven, not sure if you have tried this pack or not. 

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