Here is a close up of the beveling or chamfering. It runs all the way around the port and around each bolt hole. Every bedded fitting on my boat is, or will be, as I get to them bedded in using this method.
Most times I just use a drill and a chamfer or countersink bit but for big holes like this a laminate trimmer is the way to go. While that bevel may look big it's really only about 1/16 of an inch..