Challenge accepted T ...
Let me dig up a photo a friend sent me of a discretely modded 206 that they saw flying around which remotely matches the description...
C206Z-6000 apparently, currently operating in the experimental category involved in charter ops after it took the scenic route on it's ferry and was seen near Brisbane on that date. Not sure where this was taken although that vista sends a shiver down my spine followed by sharp, involuntary gagging for some reason. I'll see what other details I can find out however I do know that tiptanks were no longer optional equipment.
I'm sure there was a particular DHC aircraft in Brisbane around that time, but can't remember which model ...
Z1