I actually started looking into while lettering decals for my own vehicle that would go at the top of the windshield, but chickened out. Just seemed like it would look tacky. Traveling billboard sort of thing.
The problem with things like this is that they need to be big enough to be readable by someone while you are traveling down the road. "Big enough to read" and "small enough to be discreet and tasteful" are likely mutually exclusive properties needed..........
