: I thought I would use strips to create the lip with a spacer the thickness of
: the rubber seal I plan to use.
: I would glue the strips in place and put a layer of glass over them.

I did it this way and found no problem with it. I didn't even put glass over it. I glued it all up with epoxy and it is as strong as could be.

: I have a reason for preferring this method. With each of the previous 3
: kayaks, the hull curled in and the deck flattened out. I managed to get
: them to line up to get a neat join.
: This time I am trying everything I can to keep the deck in and the hull out.
: However I am concerned that if they don't line up better than before, the
: extra stiffness of the hatch lip will make it very difficult to pull the
: deck in narrower if I fit the lip before I join. So instead of pushing the
: hull out a little and the deck in a little, I would have to rely entirely
: on pushing the hull out.

I would do it before you push and pull at the deck. The spacer and the lip will create a very non flexible area on the deck, so the lid will be at the right curvature anyway. If the deck has tension in it, I would draw the hatch on the underside, and would put braces to fit the underside of the hatch before cutting so the hatch lid wouldn't change shape.

: Another related question. Why do people fit the seal to the lip rather than
: the lid? Isn't it more susceptible to damage there as things are put in
: and removed. Or is it not really a problem anyway?

Perhaps as the seal could provide another barrier the water must pass if on the lip, wheras if the seal is on the lid, the porous joint is on the bottom.

JohnK