I use the same bag, but I have the base MTX Explorer rack. Works fine for me - I load my laptop (in a sleeve) in one of the panniers, clothes in the other, lunch, patch kit and other miscellaneous stuff in the main compartment.

Only problem I have is: when I am not using the panniers, and the bag is not loaded, it can rattle a bit in the rails. Easily solved by sliding in a piece of paper under the bag when I'm latching it to the rack.