Water tight and detachable! I gotta see a drawing!
A bunk under the c-pit was seriously considered here. But that would require some serious rebuilding for supporting the cockpit sole, don't you think. Couple with that, as Kurt pointed out, it could be a very wet area.
Quarter berths tucked on one or both sides like Ebb has done are alot easier to accomodate. If we just had another 4-6 feet we could do something on the order of this...