ericlowney 

Well I opted for the Carradice Cadet - it was the smallest bag that I thought I could reasonably fit my laptop in. Tonight was my first ride with it installed and loaded, just a quick grocery run, but so far I am VERY happy with this bag. I think it fit a surprising amount of groceries in it and it's slightly narrower than my handlebars (so if my bars can fit through, so can the bag). I'll be commuting in with it this week and am excited to not have a bag on my back!