CJ and RINKER,
The cause is not yet known, AFAIK, so please do not jump to conclusions.
dickmct - "
do not jump to conclusions." Precisely - there were NONE on my part other than knowledge of, and consideration for, past incidents/accidents.
I would suggest that your background and experience, more than any other, would have pointed you to the huge difference between yourself and a trainee or low-timer, in what your description indicates as requiring both
specific skills and techniques.
"over-controlled leading to PIO and a divergent phugoid followed by a push over into negative G. This was a killer. The push-over still is a killer" I'm reasonably sure that basic aerodynamics and physics haven't changed all that much in the last century.