My first thought is "MY GOD, is that car beautiful!".
Answer to Bob's question has even more questions....
All heat exchangers have a flow rate where they work best at sheading heat.
If the airflow is EITHER too slow or too fast the efficiency drops.
There's also the question of ambient conditions and just how much heat do you need to get rid of.
Streetcar being used in a sporting manner I'd probably try rear opening louvers.
Track car at WFO probably an open hole.
I would try to get decent data to verify the louvers were enough.
I'd make my exits on the front pan back as far as I could make them.
I'd also look into "flat flooring" the front section of the car much like a splitter without the ledge sticking out in front of the air dam. Splitters create vacuum under the car and that might be able to be utilized.
Flat floor, move exit as far back on pan as possible, try louvers first for medium/low cooling needs.
Most important thing is to make my car look as good as Bobs...
That's gonna be a BITCH!