You get a number of transporters (standard, emergency, and cargo) equal to half the ship's size, rounded down. For every point of space you spend, you get another allotment equal to half the ship's size, rounded down.
For example, a size 5 ship will receive 2 standard, 2 cargo, and 2 emergency transporters as it's standard allotment. If you spend a 1 space, the ship gets another allotment of 2 each (for a total of 4 each). For a second point of space, the ships gets a third allotment (total of 6 each).
Davy Jones
"Frightened? My dear, you are looking at a man who has laughed in the face of death, sneered at doom, and chuckled at catastrophe! I was petrified."
-- The Wizard of Oz