Two points to consider:

1. You're right, you'll have splashing in rougher conditions unless the yak is so bouyant to float over versus through any kind of chop, IMHO it'll still be a wet ride. Then again, I'm thinking about where we generally like to paddle and the paddle events we like to organize out here on the open coast...

2. In real rough condition, the hard hatch over neoprene soft hatch, a somewhat common hatch closure aproach on many commercial yaks can have the lid lifted and flooding occur!! (picture the Titanic...) How do you think the hatch should be secured to prevent the lid being lifted without becoming a return to the existing methods? Chip has invented a really neat idea...check out the All-New, Deluxe Sandresky Hatch. Or here's a thought...a hatch framed like the SOF frame components sitting in a stepped wood ring, the wood ring tying into the frame? Securing the lid down by having a length of cord come up through the hatch and cinch it down with some kind of carved bone cinch block to preserve the native look?

or maybe I should just stick to strippers and shut up??