I may be wrong, but I have the impression that CASA will "approve" (if that is the right word) anything as long as it published in the company operations manual. The procedure may not necessarily be in the manufacturer's POH or may differ from the POH, but as long as it is written in the Operations Manual where CASA can nail you if things go wrong, then that satisfies most FOI's.
The book by Kas Thomas called "Fly the Engine" has this to say about run-down times. If you haven't read the book, it is (was?) available at pilot shops and he also wrote Personal Aircraft Maintenance (1981), Aircraft Engine Operating Guide (1985), EGT Systems (1989), and The Major Overhaul (1994).
Face into wind and keep the engine running. Don't be in a hurry to shut a turbocharged engine down..always idle 4 to 7 minutes (depending on OAT) facing into wind to allow circulating oil to carry away heat from the turbocharging bearing housing.
Idling I suppose is just that - the book says the engines should idle 650-750 rpm. Woomera, by the way..I don't fly Chieftains so don't blame me for the instances that I have noted in my original post. These are purely discussion areas. And as for someone saying that all company Ops Manuals agree with recommendations published in POH - don't you believe it.