I've been trying to avoid sick coworkers all fall at work, but they finally got me. Not a great weekend overall, but I did manage to get some work done on the tank this afternoon and am happy to report, it's nearly GO TIME now that the sump is done!

I got proper bulkheads on the drains from the tank into the mechanical filter. I also got a gate valve on the syphon line so I could adjust the height of the overflow and the noise is greatly reduced from the water spilling in. From left to right, return line, syphon drain, durso drain, filter emergency drain, and the emergency tank drain.

I also got the third wet/dry tower done:

The new one is a little larger than the first two to take advantage of the extra space. Since it sits over the pump, I cut the lower front for the water discharge rather than straight through the bottom, as the first two are setup. The idea was to avoid turbulence/bubbles being sucked into the pump, adding noise and/or causing bubbles in the main tank.

Each tower has an uppermost section of bioballs and a lower section of Poret form pieces (large chunks I had left over from a past hamburgermatten filter project. I keep finding differing opinions on how much biomedia is necessary for a setup like mine, so I just tried to fill it up as full as convenient. Overall, the wet/dry media volume is ~22 gallons. The Poret foam serving as the mechanical filtraiton is nearly another 5 gallons. I also have a 2-3 gallons worth of ceramic media I'd put in currently running tanks to help jump start the cycle which I'll add as well when I move the first fish in. I'd like to think it's more than enough in the end.
When running, both layers are out of the water. When the pump is off, during a power outage for example, I placed a syphon break on the return line in the tank such that it'll back syphon and fill the sump to a height which will keep the lower 1/2 of the wet/dry towers submerged, keeping the bacteria alive.

Right now the water temperature is about 65F and the heaters are running. I'm not sure how long I'm going to wait before moving fish into it - maybe until next weekend. As I mentioned, I have media right now in running tanks with bacteria on it, plus I could run some existing sponge filters on a temporary basis in the sump as well.
Things that still need to be done eventually:
1. Finish trim on the front side of the display now that I know where the water level resides.
2. Think about what to fill the gap with between the tank and the wall to cut down on noise if possible.
3. Add more lighting
4. Cover(s) for the tank
5. Cover for the sump
6. Shelving in the sump area to make up for the storage the sump and tank displaced.