The original windows on the Newport 16 were fixed port lights. The 1/8” Plexiglass is held in place by a plastic frame pop-riveted into the cabin side. The seal is a silicone bead under the frame. Unfortunately over the years the frame has cracked. The strength of these windows is questionable. The seal eventually leaks. I am not a fan of a wet sleeping bag. Later Newports made by Gloucester replaced the fixed windows with Beckson opening port lights.
I was able to purchase a set of used Beckson portlights on E-Bay. The gaskets were in a very good condition. I started the repair by removing the old portlight and sanding off the gel coat to expose the raw fiberglass. The fiberglass is fairly thin in this area. The removed portlight was used as a template to cut out a 3mm plywood insert. Small wood blocks were used to hold the plywood aligned in the hole. Fiberglass tape was applied, blocks removed, holes filled and the entire house side was covered with a new layer of cloth inside and out. The Beckson trim piece was used to lay out the postion of the new hole. To further strengthen the opening another plywood ring was cemented inside. Both inside and outside was sanded and faired to the existing gel coat. I had some graphite tape left from my Kayak Building days. Strips of that were put over insde stay blot holes to strenghten that area. Epoxy primer and Polyurethane top coat was applied. 
I tried to keep my clearances tight to reduce any openings. The portlight was set in place with 3M Sealer and bolted. The exterior trim coverpiece holds only with sealer.To hold the portlight in the open position I installed a single D-Ring that slips over the locking tab. Insect screen fits under the gasket.
