You're jumping ahead a bit. I think if you shortened your stirrups a hole or two, it might help you stay back, more upright and allow you to wait for your horse to jump. It's hard to describe, but think of keeping your body in such a position that your head is always over your feet, even while jumping. Think about closing your hip angle to push your butt back and opening your elbows to provide a good release rather than tip your body forward on takeoff. Easier said than done, but that's the goal as I understand it. Gymnastic grids help me a lot to keep from jumping ahead.