When stuffing drybags, you'll find that slightly more length is more valuable than slightly more width. 20" with a 1" lip gives you an 18" hole, which is plenty long. How wide a hatch does a 2" inset give you? You probably don't need a lot more than 12"--your hull depth/deck height will be a limiting factor of the largest diameter drybags you can fit.

Your hatch lips will not only support the hatch, but will also provide some strength where you've cut away the deck.

: I've got my hatches masked off and marked and intend to cut them Saturday
: morning. Before I do, just a quick gut check. Can they be too wide or
: long?

: My boat is Jay's Outer Island. The hatches are sized as follows... Running
: parallel to the boat, the sides of the hatches are 2 inches up from the
: seam - no variation along the sides of the hatch. They run 20 inches long,
: then the corners are rounded over using the curve on a roll of masking
: tape as the pattern, and then it runs straight across the deck to the
: other side. So, it's more or less a rectangle with one end wider than the
: other, and the corners are well rounded.

: The two things I'm concerned with are;

: 1. Is 2" far enough away from the seam? Not so much for working the
: seam, but for maintaining deck strength?

: 2. Is 20" too long? It's king of hard to tell from pictures how big you
: folk's hatches are.

: The rear hatch is pretty much the same.

: Thanks,

: Rick