Here's another option for you if you are riding solo. You have that passenger area sitting there and not doing anything, you can fill that with either a Lazy Rider Bag http://www.lazyrider.com/
or a Cruiser Bag http://www.cruiserbag.com/
And you get a bonus with it.. a backrest!
I made one of the best investments ever by installing a Givi V46 case on the the luggage rack (http://store.azmusa.com/v46mocaflbll.html
) using the Universal adapter plate. (http://store.azmusa.com/e2unadplat.html)
. As I am hauling a laptop around I needed something and this works great. I'm looking into building custom mounting hardware to mount Givi sidebags as well.