NSTG8R
Elio Addict
You don't want to do that, putting in louvers in the belly pan would defeat the purpose of it for aero by introducing air into the area under the car; you would want the venting on the side of the engine compartment if it needs it; or you could do venting into the low pressure area towards the outside edges of the windshield, pointing them into the side airstream.
A nicely designed vented hood ought to do the trick of getting the hot air out of the engine compartment. 'Might' actually help the aero [over no belly pan] if the angles of the louvers are correct. Maybe a ducted radiator shroud to smooth the airflow out the top. Man! I really need an Elio to play with!