[JP Noonan]

Make a jig that outlines the size of the opening you want to match the Lexan. Use a router with a straight cut bit to make the hole. Then either use a ball bearing guided "rabbeting " bit, or make a smaller jig and cut a ledge the thickness of the Lexan. Use silicon and rivets or some fancy countersunk hardware.

Don't know if, like others said, weather or not the top is thick enough to do this though.