Try this article:
I did it following don Casey's excellent book this old boat. Came out great.
Acrylic is more scratch resistant, but far weaker and only a little cheaper. I used screwed in 1/4 inch acrylic because I couldn't find a local source for lexan, but if I were going offshore 1/2 inch through-bolted lexan would be my choice. Check out don Casey's book it gives the formula for hole spacing and distance from the edges. Just make sure you use a really dull drill bit for the holes, and a jigsaw blade that is meant for plastic, otherwise the stuff will crack. Drill the screw holes oversized to allow for expansion. Do not use silicone, use butyl. It is easier to use and lasts longer. A router with a rounding bit will round the edges just fine, then use 400-800 grit paper to get it shiny (if u even care about the edges being shiny).
My ports had been leaking like sives for years, the po never fixed the problem just put a bucket to catch all the rainwater. So the ply core had delaminates and begun to rot around the edges of the existing ports. I cut away most of the rotten parts, so I wound up with oversized ports.
Use tinted because it looks better and keeps the cabin cooler in the summer. It is easier to hide the cut out as well, because you just paint the acrylic black in all areas except where the ports themselves will be.