I built the hatch lips using the technique described on the One Ocean Kayak website.  Normally, the lip would be built on the underside of the completed deck, but since the hatches of my S&G are in perfectly flat panels, I could build the lip on any flat surface.  I had a piece of plate glass that worked just fine.  I taped the pattern for the fore hatch to the underside and put a coating of paste wax on the top side.  I ran a length of 1/4" x 1/2" weather-stripping along the perimeter about 1/8" in from the edge of the pattern.