Hmm, crews don't have to be all that big if you have people who happen to have a great deal of skill in battle. The straw hats are small compared to other crews but they are deadly. My current crew I would be looking at would be about ten to fifteen people who aren't that great in battle but will be npcs and then one or two other pcs. Of course, about five or six of the crew men would be working the mast which leaves about three more to work in the cargo deck and a few more to be kitchen workers and so on. I am not saying that the ship couldn't hold more but we have to consider that pcs will be more powerful then your average crewman.