+ 1 for Arkel. I've been using the Commuter rear bag since it has a padded sleeve for a laptop, plenty of pockets, a handle & clips for a shoulder strap. I've loaded it with books, laptop, U-lock until it weighs 25-30 lbs and it still doesn't make any difference to the stability of my ride.
__________________
centexwoody
They're beautiful handsome machines that translate energy into joy.