By this evening, the glue holding down the power supply had fully cured, and I decided to remove the glands' rubber O-ring seal, and replace it with more of the adhesive I used for the power supply. In addition to being water tight, now the plastic rings on the inside of the box are thread-locked to the glands, preventing them from working loose over time.

Since that was self-clamping, I then got to work installing the IP67 connector pigtails through the glands to the power supply. I know you're not supposed to place more than 2 wires in a crimp-on ring terminal, but in this case, I did. There are the power and ground wires from each pigtail, plus the power and ground (a twisted pair from a Cat-5e cable) going to the Arduino. This crimped solidly into a 16AWG terminal.

I also wired the mate to the IP67 pigtail to an extension, and then to 1 string of my GE Color Effect Lights. This extension will allow the controller to set on the ground, while the lights are clipped to the gutters about 10 feet off the ground.

I connected the one string to the controller and fired it up! All my prototyping on the bench paid off - it fired up first time! I tried both outputs, and they both work. I still have one more string of lights to wire up the extension and the IP67 connector to.

I also want to find some way to secure the Arduino inside the box. I've contemplated gluing it down, but would like to be able to remove it if necessary. Also, I need easy access to the header pins in case i want to reprogram it with new patterns.

But overall, I'm thrilled with how this has turned out so far!