well done jeffroy and Dodgy,i fully concur.We found 15 degrees in the old circuit car(doing 15 or more laps)by closing off these areas and giving the air flow no choice but to go where it was told.
I must admit i was put onto it by a motor racing engineer and his reasoning seemed perfectly logical,after all look closely at a Supercar or even any new production car with a pissey little radiator...theres plastic shrouds and venturi's everywhere to direct flow to required areas.