I started beveling the deck holes several years ago on the advice of someone and would call it ESSENTIAL not just a good idea. My plate type chain plates were chronic leakers. There was a flat SS escutcheon plate on the deck that I took off every year to two to try and stop the leaks. Once I beveled the slots (and the screw holes) and used butyl they stayed leak-free for 10 years until I sold the boat. Maine Sail's article is superb.