did you look at the chrome sultan? 2400cuin rolltop backpack. if you don't need the quick in/out of a messenger pack why kill your shoulder. i have the Ivan backpack but i don't use mine very much since i don't carry around a laptop anymore, but when i did i had: a laptop, full change of clothes, shoes, pump, lock, 15mm wrench, multi-allen, extra tubes, patch kit, and a lunch.
all of the bike tools and wheelgoods fit in one outer pocket and anything else, wallet keys, phone, etc fit in the other outer pocket. smart packing kept my clothes folded nicely, my shoes from getting anything dirty, and my lunch from getting squished. and i had room to spare. i really like it, but i just don't need that much bag anymore.