And to compound this sizing method even further, some people physiologically prefer wearing a hip belt higher (above the iliac crest) than lower (on or below the iliac crest.) With a heavy pack, this repositioning might occurr several times a day for a given individual.
And so, historically, how do you "prefer" wearing your pack?
Personally, at 6'2", and using the ArcBlast for just a few months now (carrying 25 lbs max.), I couldn't imagine having anything smaller or larger. But in all honesty, the fact that I'm NOT carrying as much weight now has as much to do with my overall comfort as the decent fit of the pack.
So for me, the large is a wonderful fit - again, for me. I stopped worrying about my torso length measurement (and bending aluminum stays) a long time ago. I just need to get "close enough" and see what the pack tells me.
Any good company will allow you to do that. If something's not feeling right, send it back.