Join Date: Mar 2009
Location: Central Iowa, USA
What I see is the root of your problem is you grip with your calves and pinch at the knee a bit over the jumps to stop your leg from swinging back when you thrust your upper body forward. You otherwise have a very solid core and posture.
I would work on "two pointing" at every gate. But instead of TRYING to hold your two point, adjust your leg position (make sure your feet are correct in the stirrup, it's amazing how much of a difference that will make) until you more or less feel secure - where you aren't necessarily working in your leg and thigh to "stand".
Try this while off the horse. Spread your legs as if you were on a horse (around 2 feet apart) and just "squat" a bit, feel the weight pushing down towards your feet (slightly on the ball of your foot, as if they were placed in an iron) and just hold it and memorize that stability. You want to then replicated that on top of your horse which come from depending on your stirrup and sinking down and around your horse.
You will develop a stronger leg, which will complement your already steady core and make your jumping position solid and active. :)