Matt there are airplanes out there with side exit louvers ... the Beech Craft Bonanza and the Carbon Cub for two examples.  There's a guy with a Murphy Moose and an LS3 engine using cowl louver exit exclusively ... here's a link to his video ... https://www.youtube.com/watch?v=QyiEAcwhirg ....
Due to some of my cooling issues, I adapted some louvers into my cowlings last summer ... here is a link to my experimentation video ... https://www.youtube.com/watch?v=khG0J6zGVl0 ...

Jeff
13B, RD1-C, EC2, 186 hrs

Le Roux, I have talked with Alex a bunch over exit louvers on the side. We are hoping to tune the exhaust dumping better to help pull air out of the bottom of the cowl. I don't see too many exit louvers though on planes. Any reason for it?