Finally closed out a couple of lingering projects.
#1: Rewiring the trailer lights. I yanked out the entire harness and used a new junction box with a whip. This gives me the ability to add options such as charging and auxiliary lighting down the road.
Here's the box mounted. This was a chore. I first drilled the holes and then realized sheet metal screws weren't going to cut it do to the thickness of the frame. Next I tapped the holes - you can see how well that worked by what's left of the 1/4-20 tap to the left of the box. I eventually drilled new holes and riveted in thread inserts.
I ran all new wire down the length of the trailer and split the taillights, following the original path.
I sourced out the correct waterproof connectors to make for a clean connection.
And everything worked the first time: