Another way to solve the problem: (1) Get a dog. (2) Get a sleeping pad for the dog. The Gossamer Gear NightLight torso length sleeping pad is just right for my 80-lb. mostly Lab (who sleeps curled up in a ball). The SitLight would work for a smaller dog. (3) Use the dog's pad to support your pack and give the dog a 3-oz. item of yours to put in his pack. You thus have excellent support for your frameless pack with no extra weight!
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May your trails be crooked, winding, lonesome, dangerous, leading to the most amazing view--E. Abbey