I've been struggling with finding JUST RIGHT panniers and of course, you just solved my dilemma.
Now, where to find the time....
I wish I'd thought to put some mesh stiffener in the back layer of the messenger bag I made for my construction class. It would have made it the "knock out" project for the class instead of just being larger and more brightly colored than most people's projects. (The project was technically to make a handbag - like I'd do THAT) I should post up some pictures of that bag - it came out pretty well, even if it is a little floppy.