When I run Formula D, I run it as two races in a single convention time slot. First race is a single lap street race for an introduction. Second race is on the Formula 1 track and how many laps depends on how much time and players we have.
With only vague knowledge on hand, I'm thinking I might be able to do something similar with Sails of Glory. First battle is single ship per player basic face-off fight. Second game is two ships per player and maybe do a convoy intercept/escort setting. If someone really doesn't want to play two ships, I have several options. An easy one is to hand that person the Victory. If there is an odd number of players, I could hand someone the Constitution and call it a pirate who has no friends just to screw with the situation. These thoughts fell apart when I remembered the Victory and Constitution won't be out until January...darnit. That's the primary reason I'm looking into getting a few extra ships right now. With the eight I get at Lieutenant level, that's only 4 people running double ships. Cons prefer you can handle at least 6 in a slot.