hi nancy, assuming that the hatches are flush to the deck, i mean they rest onto a lip , then I see no reason to not screw/bolt the straps as close as you want as long as the hatch can sit under the webbing strap. Does the screw press down on a finishing washer? 3/4" should clear the edge of the finishing washer. The only problem with putting a screw and bolt through the seam , I think, is that the webbing will stick out a little on the edge of the boat. For strength worries, simply epoxy a little square patch of glass tape inside at the seam.

If none of this makes sense, or I'm not clear, another cup of tea will always be nice.