This adventure was a lot of fun! It is also easy to modify for a 5th player. Cut map #4 in half, and on the left half use MS Paint to draw a little inset map of 4-5 islands with pirate names like "The Parrot's Nest", "Trader's bay", or "The Shattered Keep". Then change the sailing riddle to refer to those islands instead of the map of Golarion.
The 5th player can use their map to help solve the riddle. Everything else is pretty easy to balance by slightly tweaking the encounters. For the pregenerated character, I added an irongut Goblin Bard named Maz who was the Ship's cook, renowned with the crew for her horrible food experiments and her friendly attitude.
