one way to make Stern hatch covers for 88 v20 ..........
17.5 inch x 13.5 inch x 1inch starboard (ebay), make template(s) of plywood and use a router to round the top edges and corner edges over, then router out the underside to 3/8 inch or so, leaving enough edge for attachment of hinges and a spring hatch support to be fastened. (L bracket or angle to underside of cap opening for support bracket if necessary). Unless you can find some replacements here.........