The only thing known about Mayflower is her tonnage, a measurement of her internal volume. Everything else is pure reconstruction. The Mayflower replica was designed by William A. Baker, a naval architect whose hobby was researching sixteenth and early seventeenth vessels. If he were alive today, I believe that he would agree that the replica is that of a typical late sixteenth merchant ship, not necessarily Mayflower.
Knowing details like gratings covering hatches are a reach well beyond Baker’s work so why bother trying to find them? Ordinary hatch boards would be just as realistic.
Roger