When I planned to do this, I was going to use some frosted perspex to get a more even spread of light and make sure it wasn't too bright to any passing Policemen.
However, because I am still waiting for my car back I have yet to start it.
I was hoping to be the first with this mod and 3 others but because I haven't had my car for 17 months now, all my "unique" mods have now been done by other people.
Be interesting to see how peoples versions turn out though.