[Raleigh]

It's hard for me to visualize what you mean, because it doesn't show in the picture. If there is a 1/2 inch gap of any length anywhere, it should be enough to allow the air to move. If it is opposite the fan, all the better. Can you feel any air coming out? If so, you may not need more vents.

If you do drill holes, it would be best to drill them opposite the fan, maybe in a row across the the opposite side. If you spread a few holes around, it would allow the air to cross ventilate better than just going across where the fan is. Since you already have a stream of air blowing on the hot component, the main thing is to allow the heated air to escape so the heat doesn't build up. With exhaust vents, you'll put more air on the component as well. Since the box won't have as much back pressure, the fan will be more efficient and move more air.

I don't know if you care if there is a fast stream of exit air, but larger vent area would allow the air to kind of drift out.