This is a trade I use to get millions by buying Gold in Rio De Janero and selling in Europe.
Once I get enough money to buy a few Vannesion Gallions... I crew my ships with the minimum sailors, remodel to no guns and all... Leaving me with 700+ free space for Gold. Go to Rio De Janero,
First Empty all food and water except for 120 water and food per ship, which can be put all in one or two ships. Buy gold there, after haggling (Saying no to first deal) and get it for $230 the first time... Load up all the Ships... Spending about $400,000 with a full fleet... Ask your adviser where's the best place to sell gold, he'll tell you. Go there sell one ship load, leave, ask your adviser again, repeat until all Gold is sold... And you've just made about $4,000,000 in one trip.