It took me a couple years of trying a shoulder bag (messenger bag has more straps?) before I decided it wasn't going to work. First I put a rack on, and panniers kind of ruined that bike, so I took the rack off and have been exploring backpacks ever since. My original intent was to get a new backpack that would work as a daypack/overnight bag and bike bag, but I found a daypack I love that cannot work on the bike, so I am trying out another backpack that does work on the bike, but I don't need another backpack maybe I should turn this backpack back (thank you REI) and try a messenger bag that will be more stabilized than I could get my shoulder bag to be.

Although the bike backpack I am using right now has a cool mesh back and channels that do some kind of ventilating. I still have a sweaty back but I think I would have that sweaty back no matter what.