Something which you also need to consider if you just lay the wooden strips on the plactic deck -- you now have the fittings sitting IN the deck as opposed to sitting ON the deck.
While the N-scale 3x3s mentioned above are only about 0.020 inches tall (seven scale inches), items such as cleats, bollards, anchor chain bolsters, etc. which should be mounted on top of the deck are now below the deck level. The height of gun tubs and superstructure are now shorter.
If the level of accuracy given by adding a wooden deck is important to you, you may then also want to consider cutting the superstructure, gun tubs, deck fittings, etc. free of the plastic deck. Sand them to the correct finished height, and reinstall them on the finished wooden deck.
That being said, there are seveal manufacturers of lazer engraved replacement wooden decks. Most are for applications where the superstructure is separate from the deck as are most, if not all deck fittings.