Here is a link to some pretty useful information about selecting and using a backpack.  Check it out – you may learn something!

http://outdoors.campmor.com/the-backpack-cheat-sheet/?cm_cat=TRAILMAIL&cm_ite=TrailMail-April52013&cm_pla=50929&cm_ven=EMAIL&utm_campaign=TRAILMAIL&utm_medium=50929&utm_source=TrailMail-April52013&utm_content=EMAIL#fbid=8JP0gnd5kIo