Very explicit - thanks so much!
My experience on the Camino (and while backpacking) is that you are right - if fitted correctly, the pack becomes one with the body!
I see your problem but do you need the shoulder straps cinched down tight?
Correctly fitted all the weight - All the weight! - should be taken by the hip belt so the shoulder straps are only to stop it bouncing around - leaving a finger or two...
I am shocked that REI could not fit you properly. In Canada we have MEC (Mountain Equipment Coop) and both my wife and I were measured and fitted with Gregory backpacks. Both packs had adjustable torso length and one had (my wife's) adjustable...
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