Paul, how did you attach your pack to your rear rack? That was my first plan as well, but I could not get it to work well. I tried to place it on the rack sitting up, but it would start leaning then fall off after just a few miles. The I tried to lay it across the rack, but then my bike was 3 feet wide and really unstable. Then I thought about making a wood platform to rigidly mount on the rack, that would be slightly larger than the bottom of my pack and try puting the pack on that, but tried a trailer first. The trailer won me over.