I use a Blackburn specific stretch cord with a Blackburn rack. I go from front, over the backpack, under the rack to the middle stay and then across the top and hooked on the opposite side so that it is held in all four directions with one cord. I haven't had any problems this way yet, but I'm not sure it is the most secure way to carry stuff. I'm looking into panniers at the moment but they can be expensive. My main requirement is that I can take it off the bike and use it as an easy carry bag without looking like a bike dork, although the helmet and gloves take care of that.