I have a smaller messanger bag that I carry my books, groceries, etc. in. But, when I bend over to grab the drops, my back arches up- since my books/etc. in the bag are flat, the bag doesen't conform to my back very well.

For those of you who are messangers, what do you do to work around this? Or, since you carry packages for a short amount of time, does it not really matter?

I would think it would be smart to create some sort of cushioning on the bag so that when you arch your back, the bag still 'hugs' your sides, somewhat like race car seating does.

This might confuse things, but here is my best quick sketch of what a biker looks like coming twoards you, carring 2 jugs of milk and the rest of his groceries in his pack.