I think It could be pointed out that most of the time the inlet holes are much larger than nessessary and therefore the outlet holes can be smaller[ Twice the size of what is needed for the inlet] rather than twice the size of the inlets ussually cut in the front of the cowl.If you had to have twice the size of the inlet for outlet holes you would be cutting the whole bottom of the cowl out. I notice in many construction pics the holes in the bulkhead behind the cowl is much smaller than the holes in the cowl itself