The double I in sportsman is two half loops with an inverted segment. So you fly past center and execute a half loop. Then fly a straight line inverted segment. The length of the inverted line is equal to the height of the half loop. The pull into the second half loop and exit.

Another way to picture it is with a box with half circles on each end. The box must be centered.

All maneuvers are described in the AMA [link=http://www.modelaircraft.org/comp/0506Rulebook/rc-aero2005.pdf]rule book[/link]