any reason to not use self tapping screws? to attach the c channel?
Yes, it is difficult to tap 6061T6 aluminum. The metal shavings tend to become a gummy mess on the tap. This way I don't have to worry about that. I just back off the tap, clean it, and continue, a couple of times. I think self tapping screws would tend to seize up. In any case I had the tap, and I knew it would work, so why risk something different?
I got the wiring from the light connector to the LEDs installed today.
I used silicone sealant to fill the holes in the channels where the wires go through, to keep them from rubbing on the wire insulation. And, I used a few dabs of the same sealant down the middle between the channels, which is a wire chase, to keep the long wires from drooping down.
Tomorrow I will wire up the matching DIN plug, ignoring which wire goes where. Then, I can connect it to the light and use an ohmmeter to identify which color goes to which LED, and label them with tape, for the next step, which will be assembling the power/controls box.