I think maybe your post might find a better response in the Private Forum or African Forum. As for my modest experience with IO 540 engines I used to fly a C207 a death trap flying around Central/East Africa and am fully aware of Density Altitude especially as the ones I flew were normally aspirated. DA in mainland europe is a loosley banded term where most of the land mass isnt 4500amsl unlike the African continent. In the case of a C207 with seven passengers and one pilot we used more runway up that a jet. And when I came to operating a piston on cold european day (-8) watching you dont over do it with the inches. But I guess your looking at folk who fly in places like yellowknife in winter! get those hot engine jackets, take the batteries in doors and sea how your prop custs into that thick dense air!