One thing to keep in mind, concerns about a sweaty back are a bit perplexing to me. I ALWAYS sweat when I ride. Even if it is cold outside, I sweat inside the layers. I have no idea how anyone could not sweat on a ride unless they are going at a very casual pace. So, anyway, I appreciate all the replies and I am indeed considering an alternative to a backpack, but not because of it being sweaty...