Just put together a Pi Hole with a Raspberry Pi 4 B. Used the official POE Hat and official Raspberry Pi 4 case. As known, found the unit runs too hot with the cover on. Runs at 102-103 F with the cover off. Went up 15-20 degrees with the cover on.
So, I found a 1" vent screen online thats used for houses and mounted it in the top cover directly abo e the POE Hat fan. It just required a 1" hole drilled in the top cover and the vent just attached by bending over the 4 aluminum tabs. It does not touch the fan. My temp now is at 103-105 F with the cover on.
Vent info in the picture.
Works great and looks good.