The ATSB report (below) has a very interesting addendum at end
It's worth pointing out that this addendum was also posted out, at the time, to all Chipmunk owners/operators as a letter from D.G. Anderson (the Director of DCA) himself.
I have posted at length about this accident (and I'm STILL appalled at the instructors' lack of knowledge - despite all that's been written over the years - of Chipmunk spinning).