Good choice on the hypervent. I used that on our Tomcat. I also put some active ventilation in. In brief, I cut two holes in the berth deck. These are about 4" in diameter and are towards the bow. They are covered with round stainless steel grates. Then on the aft end of the berth platform (where it turns 90 degrees and there is the vertical face, I cut a hole in there. Just behind that hole, I mounted a duct booster fan. This is a fan that is intended to be installed in a home duct to increase flow. I put that behind a grate and the fan blows out into the cabin. It is switched off of my 120V shore power system. When it's running, it pulls air through the two vents that are under the mattress (pulling through the hyper vent) and exhausts that back into the cabin. E.g. it circulates air under the mattress and under the berth platform. I leave it running whenever I'm attached to shore power (which is 95+% of the time). That fan has been running fine for 8+ years now and does a good job of keeping things circulating in those areas.