Having had a 1987 Cuddy from a different manufacturer, I can tell you that mine had a hole like you describe. It had an Aluminum "Z" shaped extrusion that was formed into a rectangle, and screwed down around the hole. The lower part of the "Z" made a shelf that a teak board sat on. The teak had grooves cut into it to make it non-slip. I don't remember if it had drain holes.
Ray
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"Knot Easy" 2000 Horizon 240 Volvo 5.7GS /SX
tow: 2017 Honda PILOT EXL-AWD
prev. boats:
'87 Chaparral 198CXL 4.3 OMC Cobra
'69 Jetstar 16ft Ski Boat, 115hp Yamaha
'68 Aluminum Jon Boat, 3hp Sears
'64 Water Wings