I would also suggest you move seat up and forward as much as comfortable/allowed (likely not an issue). In these pictures the seat is too far back to be ideal (because we were trying to get him used to UCI positioning - changed our plan now). Try to keep the elbows in. Also shorter cranks may be better as the knee does not go as high. Since the kids were forced to learn this for TTs, it crosses over to the road and very helpful skill.