Some quick thoughts after skimming this thread:
*The stats actually indicate that for 60-100m races it is actually BENEFICIAL to be less than 5'10". Sometimes things are not always as we might think.
*As I've pointed out several times Powell's major advantage seems to be his incredible speed endurance. This may actually have something to do with his height as there appears to be a positive linear relationship between height and sprint distance. That is, 60-100m specialists tend to be shorter, 200m sprinters slightly taller, and 400m even taller still.
*Leg strength is important because it basically creates a stiffer spring. The legs of a good sprinter essentially act as springs as the athlete bounces down the track.
*If an athlete is to continue to increase their speed they will need to apply large forces in decreasingly smaller periods of time.