radiator exit path with undertray

[lunarhighway]

i'm wondering if i should design in an exit path for the radiator air in my undertray, wich will cover the chin in front if the engine and the wheels, but might extend below the engine at a later stage. as such it will be blocking of the most obvious exit route for the air that passes trough the radiator.

since i don't want to complicate the design beyond what i can handle i wonder if leaving a path open to the wheelwells is a good idea. this would allow for a totally flat undertray and the lower pressure in the wheelwells would draw out the airfrom teh engine bay

however haveing employed dams to keep the air away from the wheels i'm a bit cautious to this approach.

the alternative however would involve some sort of duct trough the botton of the tray, wich might add even greater drag, complexity and weight to the design.

my main goal is to decrease overall drag while maintining or improveing cooling as it is.