Just a note: Variations in riveting and rivet finishing could also cause weaknesses.
It appears that several loose rivets in a panel could be enough to set up a chain of events that would lead to major failure of structural integrity. EG:A pilot would be doing his best to pull out of a high speed dive-when some skin blows loose and puts extra load/vibration on something else which then fails. He might not see the panel come loose first but if a wing or control surface left he would report that if he survived. Since different ships had differently located problems the rivet thing may be responsible for some of this. If I recall, North American was concerned about over-speeding and experimented with speed brakes which were of a latice configuration that deployed from the upper wing surface near the trailing edge. An engineer also told me that they had figures for how much skin rivets influenced the "tightness" of the whole structure. A ship that had a really good rivet job would likely have an edge on one that did not.
