[Franco]

take a grinder to the inside edge where the original plywood was bonded to the lid. cut a grove all around the lip - peel off the inside and discard - scrape and then grind the surface smooth. cut squares of plywood
( the squares allow the plywood to conform to the shape better) to fill that void. cut a piece of fiberglass cloth slight bibber than that surface, wet down the inside with fiberglass resin, lay on the cloth, roll it to get out the air bubbles, mix another batch of resin, and wet down both the inside and the pieces of plywood as you place them. the should be fairly snug, cut some more cloth and wet down the top of the plywood, add the cloth, add some more resin and roll out the bubbles. you can cust strips 8", 6" and 4" wide to layer the perimeter for extra strength. Then cut your holes for the deck plates. Seal the edges of the plywood with resin brushed on. use 5200 when installing deck plates TADA!!!