I took the survey. I do use a messenger bag (medium Timbuk2) and I am definitely a small person. Fit wise I don't really have any problems with it. The medium can take just about any load I can carry (I've had over 30lbs of cat food in it.... and it didn't break). The only time it flops around a bit is if it is empty. I have added a lot more reflecty bits to it - when its full it does cover much of my back and I'm sure its the first thing people behind me see.... so I put more reflective material on the bottom, since that is what actually shows when I'm in a cycling position.