Bring your toes in a little. Use your calf not your knee. I'd get more contact in the reins, but keep your hands where they are. Roll your shoulders back just a tad bit. I arch my back a little when I jump too. But I try to push my shoulders back a little bit when I can. The horse is using its neck really well. But it's legs aren't up enough. Are you riding with your seat towards the fence? If you are doing a half seat, which is okay, sometimes its good, sometimes not. Use your seat like you would in dressage. Push the horse up into your hands and ride the horse to the fence. It helps with leg position and rein length too.
I like how in both photos your position barely changes. I think you look pretty great though. :)!