Since I am going to go with an Ocean style cockpit, any suggestions on the size? I did a quick look and I didn't see anyone offering spray skirts but I am sure they are out there. I just don't know where to look. I have seen 16" x 20" size mentioned several times. I have seen what looks like a keyhole(?) but is much smaller in Ross's Kayak Foundary. No need to reinvent the wheel. So whats standard?