thanks JoeG. I bought a Topeak trunk bag from amazon, its similar to the Axiom with the fold out panniers. The problem I had was the rack on the bike is narrow (a bit over 4 inches wide) and the bag velcro straps are mounted about 5 inches allowing the bag to shift on the rack, but I was able to figure out a solution and now it doesn't move on the rack. I have a bit of weight in the bag including the ABUS folding lock (I know it can go in the storage compartment) so didn't want it sliding back and forth. Did you have a problem with your trunk bag shifting??