I'm confused the Comfort Rating charts – are they explained somewhere? How do the frame extensions affect comfort rating?
I'm considering a Divide 4500, and have a 21" torso. Most of the time I'll be carrying 20-30 pounds, but for an upcoming 2-week Grand Canyon hike, will be carrying 40-60 pounds much of the time. I assume I'll need extensions – which size would you recommend? And what comfort rating would that work out at, at 60 pounds?