Nice mapping.

You might want to swap your downstairs tiles over. The perspective makes it look from the bow side like you are stepping down from the forecastle deck to the main deck through the tile square and for the stern side the angle would have to be impossible to get down to the space under the quarterdeck. In fact you don't need those tiles at all, just a doorway next to the upstairs tiles on each side to give you access to the main body of the ship.

(Yes I know stairs go both directions but it's easier to designate the stairs from the main deck to the other decks as 'up' for clarity.)