Why not just velcro the thing in a shape of a tube and then attach that shoulder strap that came with your laptop case that is collecting dust in the closet? If you're carrying a change of clothes get a messenger bag (mine is a Chrome that has a built in feature for tube carrying) and strap it to that. This is much more desireable to sticking out so far. With a messenger bag everything is at an angle as oppose to hoizontal so there is less lateral space being taken up. I have also transported long items by stapping them to the horizontal bar between the seat post and the handlebar neck ( what is that called anyhow?) The item stuck out front without getting in the way of steering.