To help reduce underhood temperatures, and to encourage airflow through the radiator and the intercooler, we've stolen a page from the WRC guys and installed an air extraction vent. Here's a view from underneath.
Top view. The badly-placed sticker is to cover up the paint job that went horribly wrong the day before a race.
2010 Update: That's a story worth telling. Myself and Sign Guy (from Signs And More spent a very late Thursday night grafting this vent into the car. Everything we tried to bond the carbon fiber to the metal refused to hold. In desperation we tried JB Weld, and that worked! Feather in a little Bondo to smooth it out, shoot it black, so far so good. Then we shot the clear coat and the paint blistered up underneath it. AUUUUGH!
So in a moment of inspired clarity, we slapped the vinyl over the mess and just covered it up.
That hood now hangs on the wall at Signs And More. He earned that one.
Later, we replaced the hood with a fiberglass model from SquidSkins. That too got the vent treatment, including the JB Weld mounting mechanism. I can't say definitively if the vent actually accomplished anything, but the car never overheated.
Trivia about the SquidSkins hood - his mold was pulled from the hood of one of the Archer Racing cars, but they didn't bother to remove the vinyl graphics from the hood before laying down the mold. Accordingly, the outline of the giant eagle from the Archer car was embossed into the gel coat of the hood. And that hood was bonded to the hinge supports using more JB Weld, after I ripped the fiberglass off the metal mount blocks when I forgot to pin the hood after tech inspection, went to soundcheck, and the hood blew open at 80 MPH. (2005 Atlanta ProSolo)
I am very pro-JB Weld.