Steve
Just to be clear, the horseshoe type fitment is the most common one I've seen, this is the one on my mate Tony Windeatts bike. I was just suggesting something a bit simpler that would not involve much fabrication.
Perhaps I'm missing the ethos of the Cannonball event, but if putting bicycle disc brakes on is acceptable, why not just pop down to your bicycle shop and get one of the LED lights which just clamp on to the handlebar and a red one for the back stay'
If you get a GPS too you'll know where you are and how fast you're going
If your 13 is anything like mine it'll barely pull the skin off a rice pudding so I don't think you need to be punching a light out front 100 yards, I still say, think like a cyclist, be visible.
Do you actually do any stages at night ?
Best
Chris Mac