Bill, perhaps a hole saw or roto-bore would do a decent job of it. Was the light bar media blasted prior to powder coating? I've found that a local machine shop uses a conversion dip process (less labor intensive) that was rather ineffective in that the powder seemed to scratch off as if it were paint. Similar jobs done with a media blast prep of the surface, and you couldn't beat the finish off with a stick.. So I would consider what prep process was used as to whether the PC will adhere well through a drilling operation..
