The other comments about thin or no epoxy are probably on the mark, but so is the thought that water probably lays in there between gasket and edge. On my Coho, I did 2 things a bit differently than instructed: 1) I used self stick, 3/4"x1/2" Frost King weather stripping instead of cementing the kit-supplied strip.- it is much easier to apply, and more importantly, easy to get off, vs.contact cement which leaves a lot of residue. It's squishy, seems to seal well. 2) I stuck it to the hatch itself, not the lip. My reasoning was, it would be easier to work on, it would be easier to rinse grit off of, and,the hatch would be less likely to slide off if a bit loose. Hearing your problem, I think having the gasket on the hatch would also let the lip dry completely when the hatch is off, rather than letting water remain in between the gasket and the deck edge. As far as leaks, I sometimes get little, but I'm not convinced that it isn't condensation- before drilling a 1/16 hole in the bulkheads, I had the hatches sucked down so tight after a rainstorm on a hot day that I couldn't pull them off, and I thought the boat might cave in.

The cam buckles can go really tight, but I don't like having to fiddle with them,and I sometimes knock a cam loose when parking the paddle. I am taking them off, and going with an external bungie- I don't mind the look, and its a snap to batten the hatches. Pretty sure they'll be tight enough.