A friend of mine went to get a BCU rating in Britain. He said the guys there weren't happy with their hatches if they didn't see the VCP hatches sucking in as the sea cooled the air in side their boats. Of course, you can burp a VCP cover to equalize the pressure.

I was thinking of mounting one of the scew in drain plugs CLC sells at either end of my next boat. I want them for the convenience of draining the boat, but if my hatches turn out airtight (not likely) they would also take care of pressure problems.

BTW, anybody have feedback on these units?