> The ply strips should work. I have recessed hatches on my Cape Charles. I used two strips of 3mm ply laminated under the deck (after the deck was in place). The bottom most strip is about 45mm wide, allowing the hatch lip to extend into the hatch opening about 20mm. The top strip is really a 25mm spacer to drop the lip far enough to allow the use of a sealing compressible foam strip. These laminates serve two purposes as they also add strength to the deck itself. You should remember to allow for the lip intrusion into the hatch area by increasing hatch size slightly - you wouldn't want to find your hatch opening too small for practical use. My recessed hatches use small frames (cut to the deck radius) to hold the hatch shape. To lock the hatches in place I use polyester webbing straps (they do not loosen up the way Nylon can), terminated on adjustable buckles. I tried experimenting with different internal bungy type closures but found that they made loading difficult, would loosen up over time, and leaked substantially. My strap tie downs do not leak much despite being subjected to the washing machine that is Sydney Harbour, and the wider Pacific coast. I found that using a compressible foam on the interior of the hatch lip to be a sufficent sealant for the hatch. This foam is a simple adhesive draft stop roll that can be purchased from most hardware stores. I use a 4 mm thickness which allows compression to deck height.

GD