Chuck I did this on my tandem flatbed a few years ago. The wiring would always hang down and get caught on stuff. Since I added the conduit, zero problems.
GM I tack welded the conduit on my tandem, and was thinking of doing the same on this one. I decided I would rather put it together, pull all the parts and paint them individuality and put them back together later. That way everything has a nice coat of paint on it.
Go get the grommet Pusher, I have found that putting things off is expensive! Or a pain or both! What you are seeing is a Tek self-tapping screw, It is actually more olive green than brown. It has an non-corrosion coating on it, I'm guessing an epoxy.
I spent tonight drilling more holes. Its amazing how many it takes to mount all this stuff. I started out by finishing up the access holes for the frame coating. Then I drilled 40 3/8" holes for mounting the steps, bunks, and guide rails. I still need to drill the adjustable bunk brackets, I took them off for sandblasting. I also need to drill the holes for the trailer wiring, but need to pick up the bigger grommets so I know what size to drill. I want to also drill the mounting holes for the lights. Basically I want to have it ready to bolt together once I have it painted. More time now, but it saves later and all the holes get paint on them.