Nice job.

Also, Planet Bike makes a bracket for racks. You could use two of them bolted to a piece of aluminum or some such material. Then bolt the aluminum to the rack. I like this idea because you can make it as wide as you want.
http://ecom1.planetbike.com/3108.html

I'm in the process of designing a bracket or light for one of my racks. My Blackburn rack does not have a bracket for lights. Also, my rack bag hangs over the edge, so I want to make a bracket that will extend outwards a couple of inches to clear the bag.