The cracking came much later and probably only as a result of our continued use of the external fuel tanks.
Not probaby, but fact. The RAAF repeatedly warned AAvn of the potential problem of leaving the external tanks fitted, and like virtually all other advice from the RAAF, it was totally ignored. In those early days after the Army takeover, you could be forgiven for thinking that if the RAAF did it one way, the Army went out of their way to do it the other way. Ask any of the small number of RAAF pilots who transferred to the Army. Sidelined and ignored would be a kind description of the way they were treated. ("Arf", are you reading this? I'd love to have you share some of the tales you told me with everyone here - or at least the ones you could tell.)
My main memory of those days is anecdotal, involving an exercise where a detachment of four Blackhawks was based on an exposed beach for two weeks. At the end of the exercise, all the BH groundcrew were tasked to wash down all the Landrovers and then sent on two weeks' post-exercise leave. Their helicopters were left, salt-encrusted, for two weeks before they were given the same attantion as the Landrovers received immediately after the exercise.
As I said, it's anecdotal and might not have happened. However, I can assure you that the person who told me, who was there, was insistent that it did.