It takes a lot of confidence to post knowing that there are a typical variety of people on here who will bring out all of your flaws; loud and clear, and I'd like to congratulate you!
Anyway, as I've been looking, there are a few things I've noticed... Especially with the comment "looks like you're pinching and holding on with your legs". This comment really is difficult and vague to someone looking for advice for a few reasons.
First of all, in order to stay on, it's pretty much a requirement to grasp. Good balance dictates exactly how much because ultimately, that is the key to jumping-balance. So when that comment, "you're gripping with your knees" comes out, it doesn't say anything other than the fact that maybe the critique-er has never jumped. (?). So, if you're looking to make a constructive comment and see that they're gripping too much maybe consider saying that.
Now, I just want to say, I'm not trying to tell you how to critique and I don't want to sound like a know it all, rather I'm trying to make these more beneficial and helpful for those looking for pointers.
SO here is an image off Google that I'd like to point out. I know that there is, and never will be, a "perfect" jump by any rider , but this one to me comes pretty close.
A FEW THINGS:
So, in this picture, I think it really demonstrates:
~The rider's center of mass is really directly above the horses back/protrusion of withers
~A solid release where the horse is reaching for the contact, and forming a brilliant bascule
~Rider's body is contoured to the horses's shape, allowing for a nice over all image
THINGS that need "work":
-Rider's leg has slipped much further back than one would like to see, and the toes are pointed down instead of heels
-The rider is further off the saddle than we'd like to see, and really has quite a bit of space between the saddle and butt. This will just promote the rider to come and "fall" back down harder on the horse.
-Looking down; the riders eyes are down over the jump which is a common fault. She should keep her eyes up, and over to the next landing or jump.
-Her knees appear to be off the saddle, which limits contact and prevents the rider and horse staying connected in the basic areas.
Things to look for and keep in mind:
-What is the horse's face looking like? Happy? Expressionless?
-Does the horse "reach for contact"? Often times the rider has a good release and the horse (if it's well trained) will reach for that contact and people commonly say, "not enough release".
-How are the riders hands?
-Riders arms and Elbows? Are the arms slightly larger than/less than 90 degrees (anywhere from 80-100is acceptable).
-Are the elbows "flapping out" or tucked in to their body?
-Rider's face and direction of looking? Is it ahead or down on the jump that they're going over?
-Where is their center of weight appear to be? Over the horses neck?
-Are the legs gripping "too much" or look too far back?
-Are heels down and toes up? Also, are the toes sticking out instead of staying tucked in/parallel to the horse's side?
-How far off the saddle is the rider's seat? If there's enough to see through to the other side, then it's most likely WAY too much. There should be at least one point of contact on the seat.
-Is the rider's back concave and arched so that they look to have a swayback? That doesn't create the ideal picture. It should shape around the horse, like in the photo above.
-The foot should lie directly under a line created by hip-knee-foot *ideally*, which almost never happes, but you could just look for how close/far away it lies.
Hope this atleast refreshes people and helps!
Thanks for reading!