: Viking Marine has 10 inch ones. I used the cam lock ones on one boat and they
: were 100% water tight and worked well. Some commercial manufacturers were
: using them too.

I've just added 2x10" as bulkhead hatches with "screw-in" and have already regretted it. I'm thinking impossible to open on a cold day, with gloves on and cold fingers. Closing is probably worse and will require a two hands operation.

The "cam-lock-ones" Jay is mentioning doesn't really translate well into neither Vikings list nor my Danish vocabulary - but sounds recommendable ;-)

Jesper,
Copenhagen, DK