ARMSTRONG 6 INCH DECK PLATE

The Armstrong 6 inch deck plates are a fantastic solution for your boat if you've struggle with the weak standard ports. In short order they leak, or you fear putting a knee or heel through the deck and ruining your day on the water. They're not cheap, but they are strong! Additionally, they seal is on the port itself and not on the hull, so if you store your ports in a bag out of the sun, the seal is protected too!
This port is great for any flat sturdy deck surface. It makes for easy and durable Sunfish Deck ports! Just jigsaw or hole saw out a port hole in your deck, smooth the edge and install the port! 
The aft ports of a Hobie Miracle 20 are often under water and prone to some leaking. Some reinforcment should be done, but with some fiberglass backing or starboard epoxied to the inside of the deck, you can cut the 5" port out a bit larger to accommodate these 6" ports. 
They are often used to replace the deck port on Farrier or Corsair trimaran ama ports! You can stand or jump on them (relatively) without issue!

They fit in the standard H18 deck port holes. You need to seal up the screw holes from the stock ports with some epoxy or other material and then you're good to go!