Ampan,
"I'm not really sure about the legal situation concerning the Chippendale and Mahon reports."
This from John Kings publication, which I am sure was very well researched and had the benefit of hind sight.
"Because the findings of the Royal Commission of Inquiry on the cause of the disaster were limited in scope, being legally an opinion and not a statement of fact, they could not be appealed in legal terms, unlike the Office of Air Accidents Investigation report, which remains the sole official account--and has never been officially challenged."