I'm trying to increase the ventilation on my Catalina 270 - I've one outgoing day/night solar fan but I've thought about installing louvered vent in one of my companionway boards. I've notice some of you say you've done this and I'd like some advice. My boards are "starboard" - two pieces. I suspect it would be best to have something that allows you to close off the vent in very blowy weather?? An help is much appreciated! Fair winds to all