If you wonder how a shorter boxer can stay outside, pick his spots and land his jab, watch my childhood hero Alberto Davila. http://www.youtube.com/watch?v=zhHYnW2tVX8
Unfortunately for the shorter guys, it's harder for a shorter person to get on the inside than it is for a taller person to keep you outside. Luckily I'm usually the bigger fighter (6'4") but it sucks when I'm the shorter fighter in the ring. It usually involves a LOT more head/body movement and extra effort.