I've just stumbled across this brilliant infographic over at Brian's Backpacking Blog, created by the folks at REI.
When I bought my pack I had been suffering from quite severe and recurrent lower back pain, so choosing the right one was essential. At the time I remember being surprised how hard it was to find solid information on the subject. It's all summed up very well here. Not to mention beautifully presented.
I'm not looking for another pack but I still need to pay more attention to the way I load the one I've got. I'll be referring to this for my next trip.
What do you think? If you've got anything to say, please leave a comment below.