I have a torso length of 18 inches. I see Jam packs on nice sales (as the new version is out), but I'm right at the size change…a small is 16-18 in, and a mediums is 18-20 in.
Should I size up? Seems like it would be better to be slightly too large, rather than slightly too small.
Personal history…I bought a small GG Vapor Trail years ago. I'm below 20 pounds pack weight when using this pack (3 seasons). I've never found the comfort from this pack that others have, and I've often wondered if it's too small.

