Roy,
2016, I removed and reinstalled the 6 chainplates on my boat. Before slipping the chainplates back through the deck, I opened up top deck slots with my Dremel changing the slot to a groove and provide clean fiber glass to pack in the Bed-it Butyl tape. I wiped the chainplates and deck area down with Denatured Alcohol. Slipped the chainplates into place. Then I filled the groove with butyl and packed it down against the chainplates. I then slipped the cover down on top of the butyl. I screwed the cover down in the prepared fiberglass holes using butyl on the screws.
No leaks have appeared in the past 7 years.