mike, by doing something to allow the air to escape easier, you will actually allow more airflow in to the engine bay, as the pressure difference between the bay area behind the coolers and in front of them will be reduced.

i'm not sure that the vents at the base of the screen are the right place to do it though normally, that area is a high pressure zone to force air into the cabin for ventilation and out through the rear inner wing areas behind the back bumper where it is low pressure.

if you allow the engine bay air into that area, i think a lot of it would be drawn through the cabin making it hot and possibly fumey (spelling, or is that even a word?)