I mounted these (
http://vehiclelight.com/0300251.html ) over the tail lights and as high as the backup camera 2 years ago. The traffic can see them in bright sunlight and beyond your toad much better and they don't get as dirty being higher. Since then I have installed them on two other Beaver coaches ( Lamar Keck and Jim Bull ).
I would like to see others with them just from the safety aspect. I position the lamps with tape where I think I want them. Then walk back and view from a distance to make sure they're even. I use a 1/2 inch hole for the wires. The only hard part is fishing the wires down to the the existing lamps. There can be fiber glass insulation to go through. I use an small electrical fish tape and feed it down that 1/2 inch hole, attach the wire loom and pull it back up thru the hole. I like using trailer wiring loom. It is coded white/brown/yellow and green and it's packaged in 20 or 25 feet. If you find it priced by the foot get at least 15 ft. I also use heat shrinkable butt connecters. It's about an hour's work if the fishing is good. Some coaches have plywood above the tail lamps to hold the insulation that you have to drill through. I use a 1 1/4 hole saw because I need to find the end of that fish tape. I hope this is complete enough to help you do this yourself. If you have questions, my phone is 707-217-0903.
