: Any rules of thumb for hatch sizes? I am going to be cutting mine soon and
: starting to think about the size. I am leaning toward an oval shape.

Nope... You can make the hatches just about any size and shape you want as long as you leave some material between the edge of the hatch and the sheer line. If you're curious, here are a few sizes of round and oval production rubber hatches.

Kayaksport (Current Designs; Dagger; Eddyline; Nigel Dennis Kayaks (NDK); Perception; P&H):
Round 5.9 to 9.5 inches
Oval 16.5 x 11.8 inches and 17.3 x 10.3 inches

Valley Canoe Products (VCP):
Round 7.5 inches
Oval 16 x 9 inches

As you can see, their pretty big!

Dan