I went with the large- 18.5" torso, I am a little marginal on the medium.

It has dividers that you can have in place or not. With it in place, there is a barrier just above the lower access. I've got a tarp, hammock and wool blanket in there right now- nothing that will be bothered by compression.
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-IronRaven

When a man dare not speak without malice for fear of giving insult, that is when truth starts to die. Truth is the truest freedom.