I took a bunch of photos of steps that I thought were not as well documented.
The best discovery in this build was someone previously mentioning and showing this toilet flange. The holes for the flange line up perfectly with the computer fan and thus seal both the flange and the fan pretty well. It also sits just inside the plastic ridge on the lid, making placement very easy.
I used #8-32 2 1/2" machine screws and flat washers to secure it, and they go perfectly with this setup. If I remember, I'll get wing nuts to replace the normal nuts on top, as they're just finger tight.
I'm going to get back to my other packing and organization now, but hopefully I'll have time to install the water level switch and another switch for inside the tent so that this is easier to operate.
Biggest problem I had was that I got vinyl tubing, which was not at all easy to perforate using hot 10-gauge wire. It is too hot in Oakland these days to be running the oven in the middle of the day anyhow! I gave up on this after hole 2 and instead pinched the tube against the table with my thumb and nipped out a tooth of plastic at the edge at each mark I measured previously using a box cutter. This worked pretty well.
Wiring up the fan and pump in parallel was a bit of a pain until I figured out how to use one butt connector to splice 3 wires.
I need to do a bit more testing to make sure no water is dripping out the holes. It seems like it helps to have the top on tight to keep the hose spraying into the duracool.
I'll try to post my other build pics this week. Thank you figjam!