Sailingdog and Maine Sail,
Thanks for the help in replacing my ports. Between the two of you, I was able to "Get'er Done".
Although I used a different brand of opening port, and didn't have a template supplied by the MFG'er, Maine Sail's tutorial was similar enough to be very helpful. And SD's advice was on the mark regarding epoxy-ing the inner and outer surfaces together. (While I was at it I replaced the wood in the middle as the old had been drilled and re-drilled several times and looked rather like Swiss cheese.)
In case anyone wants to hear the details, here are a few :
Removed the old ports (4 ea).
Cleaned the old silicone sealant.
Refurbed 2 original windows with new acrylic and new seals.
Removed old wood from between the inner and outer walls, and re-epoxied new wood in place.
Made my own template to fit the 2 new opening ports.
Located the template and then routed the 2 new openings.
Dry fit the windows.
Cleaned the outer surfaces again.
Installed the butyl tape on the mounting flange.
These windows had an exterior flange, and an interior trim ring. The exterior flange has no holes. The holes in the trim ring lined up with holes in the window frame. The screws clamped the cabintop between the frame and the trim ring.
I installed screws in all the holes before tightening them to "a little snug". I then did the other port the same way. Then I went back and forth tightening the screws a little at a time while also reinstalling the 2 original windows. This was to give the butyl time to squeeze itself out evenly, (as per Maine Sail's suggestion.)
Trimmed off the excess buytl tape.
Now the cover is off and the rest of the season's work can start. Oh yeah, and it is raining this morning so I can go see how well I did.
Thanks again for the help, SD &MS