This could be just me, but I'd like to see a bit more consistency in the release. A couple times you were on, but a couple it was a bit late. It could be that you are riding defensively because it is a green horse, but I agree with the tense back and heels. It makes your entire body become unbalanced and is the reason your landings might look a bit off to you.
MBP- you are right, just a bit of relaxing to make the whole enchilada a bit smoother to improve the rider,but I have to disagree on the dirty stop. If the rider is bracing to the point of being rigid, it is much easier to unseat than a balanced seat.
Good luck, happy jumping!
We are not human beings having a spiritual experience. We are spiritual beings having a human experience. -Pierre Teilhard de Chardin