Thank you, George, for that additional bit of information.
That is now added to my list of things to check when I return to my engine builder tomorrow. And that one seems to be a pretty easy visual check.
I have sent an email back to the CHI representative, outlining with photos and text what I have discovered and requesting that he actually contact their engineers for their feedback. I also specifically asked for him to check on the spacers you said they once offered.
Do you think it is possible that there were slight differences between the USA heads and the Australian heads? This might explain why they do not believe there are any changes in their design, if Australian heads were used as their base point?