To expand more on that. I now believe that opening is a no teach. If you teach to have good drive mechanics and the arm circle has a good path everything opens by 12:00. The trick is to allow them to close some but to hold it still through release. Java's words: "...the energy required to move the mass of the torso is energy that could have otherwise gone into the ball. Geek version: Proximal stability creates distal mobility."
Instead of teaching to get open. Teach drive in the beginning, and teach to resist rotation through release.