> I thought the hole was supposed to go in the middle of the bulkhead so
> that even if you're upside-down water wouldn't go into the hatch. Should
> it be the top or middle?

What you'd like is to have the hole metacentrically located --- essentially, at the center of flotation. Another way to visualize this is to imagine the hull sealed up with 20 gallons of water in it; as the boat is rotated on its longtitudinal axis, the water will rise on the bulkhead at different levels --- highest when the boat is vertical and the fixed amount of water fills the hull at the position where the hull is most narrow, lowest when inverted, filling the hull where the deck is widest. The center of that area --- and, not coincidentally, the point where the water is least likely to flow into your sealed compartment --- is the metacenter of your bulkhead, and an excellent place to locate a very small hole.

Jack the English Major!