I saw your video on You Tube, but I can't reply to it, I have to start my own thread. I'm writing this to the person who was riding the 7 year old who did not actually belong to the rider.
To the rider:
Your position was pretty good, you did not catch your horse in the mouth at all which was nice to see, however, like many riders you 'ducked' forward to much with your upper body which meant that your lower leg slid back over the top of each jump, making your position insecure. Imagine if your lower leg had flown back and your horse stumbled on landing, you would go straight over your mount's neck as you would have nothing to brace against.
If you sat up straighter over the fences, I'm pretty sure it would solve this problem. Your horse looks good, he snaps his knees up nicely!
If you corrected your lower legs, you would be almost perfect. You should so take your horse to some shows as you could do very well together.
By the way, I love your cool arena! I wish I had facilities like that, I'm stuck on a race track or paddock.