Update on the solar-powered exhaust fan:
The Deltas didn't work out. They have an excellent current to airflow ratio, and have an incredibly low startup voltage, but I didn't take into account that a higher-amp fan would cause the voltage to dip more on the panels. My 120mm Yate Loons actually spun up with less light. I ended up ordering a
92mm Akasa branded fan which needs only 0.05amps and pushes around 30cfm.
I'm planning to use both of my panels in parallel to power the fan, and put them in different locations. Direct sunlight on either will power any fan I put on it, but due to the tinted windows, I'll need to experiment with placement a bit. When the panel is out of direct sun, the power output is only a tiny fraction of maximum, though both together will spin up this fan in bright indirect light.
I went out to the car with a drill, prepared to add 4 holes to screw the fan into place, but after looking at it a bit I decided that zip ties would work just as well, without the need of irreversible modification.
I left a gap at the bottom so the battery box can still vent on the driver side, but added some tape around where the fan sits to help develop enough pressure to push the baffles open.