Vents....
...I assume you are talking about ventilation with the hatches closed.I'd install a 3" solar powered intake vent on the foredeck over the V-berth and a 3" solar exit vent over the head. My hatch boards have louvers in them, problem is they are covered by canvas when I am away from the boat,I have seen passive or battery powered exit vents mounted on the hatch board. That is an option, I guess. If I wanted a third cabin vent I would consider a small passive or battery operated exit near the galley or maybe right on top of the main hatch..