When I use my backpack on the rack I take the stretch cord and go across the top, then under the rack to the center stay, and then across the top and hook it onto the opposite side making a cross on top. I make sure that all straps are tucked under and also make sure the strap ends are tucked as well. I sometimes did it face up and sometimes face down. I never had any problem with this setup except that everything is inaccessible while it is strapped on and I put everything in the backpack. I did this for my first 3 months before I decided I wanted something else that was more convenient. The Knog bag works well as both messenger bag and pannier, has a protected laptop pocket, holds my clothes comfortably, and has lots of pockets. It easily adjusts so that my heel doesn't hit it too. The one thing I don't like is that the bottom waist strap doesn't work as a bottom anchor for the pannier. At least that strap is removable and I can probably find something that'll work better.