The first thing when trying to run fast on stilts is that it's not so much running but jogging
Don't try to run has at first you will end up dragging your hoof alone the ground and tripping over.
Becuse of the power of the spring action you will find you need to bring the knee up has you would jogging, this may sound like you'll be slow but you'll be surprized how fast your going !
Has you jog lean forward a little to gain more speed. Once your jogging like this you can then try not to left your knee so high ( watch out that your not dragging your hoof ) this means you can kick it down more and get even faster.
Another thing you'll need to learn is stopping quicker !? The first time I got any speed up I ended up grabbing a sign to stop running !?