I have had a 22" Ebay bar on my truck for a few years now. It is mounted inside the bumper opening on my Dodge (between the tow hooks). I welded some flatbar to the base of the hooks for mounting.
I kept the wiring simple and added a relay driven by the high beam circuit so that the bar comes on whenever the high beams are selected. Of course the bar is not DOT approved, but driving into oncoming traffic isn't legal either... I can toggle the high beams off quicker (muscle memory) than I can reach for an aux switch elsewhere on the dash.
Mounting the bar on the roof using windshield mounts is a terrible idea. A friend did just that. Wind turbulence caused a bunch of cab noise at higher speed (on a truck running 37" mud terrain), and the light was near useless because of the reflection off of the hood. He even vinyl wrapped the truck hood with flat black, which helped, but was still hard on the eyes. He ended up removing it.
