I already have something that does the same thing....the side rail ! used it all the time on my speedmaster. Thats not what i need however.
the side rail! that is how I managed to run my backpack and the laptop inside it thru the rear wheel of the t-bird (few weeks after I got the bird). Hooking bungees under the t-bird rear fender is not the same as the speedmaster, the t-bird goes straight back, speedmaster curves down. So even tight bungees slide right off the bird.