Just an idea that you can run with. You need air flow, not just holes. In the photos you can see the scoops on the side, those function, there are holes just smaller then the scoops under then. The air flows through those over the battery and ESC then I made a wood directing baffle so the air flow is directed out the bottom of the plane. When I land my battery and ESC aren't even warm so the system works pretty well. The CUB has the engines out the sides so just do a little thinking and you can come up with something that works and you don't notice.