Good just wanted to point that out. If you think the outlet area is a little small then it would be more effective cooling wise to just open the bottom up some and not vent the sides of the cowl. This way you have what is called a pressure cowl but venting the sides would tend to slow down the flow through. This has the added advantage of by just opening the bottom a bit is far more attractive than the vents.

Doing vents the way you described is likely to come out looking real ugly and even hinder the cooling, let the air out at the bottom rear if needed.

John