I'm trying to get my plan in mind on how to do wiring tasks. First the light has only a short white positive wire.
So I've decided to use red wire for all positive power wires and black for ground. This will be my standard.
Next I decided to just butt solder the extension wire to the light. I can't see any need for a disconnect and wiring book says this kind of joint works great. So I opened the threads, interlaced them, and soldered them together and then covered with two layers of shrink wrap.
Next decision was to use local grounding. So I removed the primer in the place I choose for a grounding plate nut. I removed primer on both sides of rib.
I also decided to simple put a rubber grommet into a pre-existing tooling hole and run the wires thru it eliminating need for any adel clamps or stick-on plates to hold the wires. I had to enlarge the hole slightly to 9/32nds.