How Big Is To Big

I often wonder how much air going into the injector is to much? Some of the air scoops on the top fuel & funny cars are humongous the blower can only pump so much air, i understand that there has to be forced air to keep the boost from coming out from the center of the rotor's, but to big just acts like a parachute and slows the car down , anyone think like this ? or can you explaine the size benefit? there has to be some logic to this that im missing.

 

the bigger it is the more ducting you can put inside it!..LOL