RE: Engine Cooling - Inlet & Exit
THe only thing that is important is teh air that is flying over the cylinders. All the rest is defeating the purpose.
I would recommend that you baffle the cowl to ram as much air though the cooling fins as possible.
If you have 1000CFM going in and only 10CFM is touching the cylinders, then the 2000CFM exist does you little good in cooling your engine.