You might notice most of the stains on the outside of the airplane seem to originate from the bottom of the hole then sweep upward along the path of the airflow over the wing. That would suggest to this untrained observer the initial punch through was there, and the balance of the hole might have been simple propagation of the failure. If that's true we can be glad the airplane was still climbing at a relatively low speed -- 350 knot winds could have done some serious peel back of the skin. .