Viperdoc wrote:
The question that comes up every year is whether to open the cowl
flaps for
start, taxi, and take off, knowing the ambient temperature is so low.
[stuff snipped]

Any other reasons to keep the cowl flaps open on such cold days?

I know of a very experienced skiplane pilot that is concerned with
overheating during long ski taxiis. (In soft snow, the power settings
are higher than taxiing on a hard surface.)

I think you need to realize that cooling on the ground while
taxiing is a whole different ballgame than when at flying speed.

I've flown with the above mentioned individual in a C185 when it
was minus 25 C and the cowl flaps were open for startup, taxi and
takeoff. He then went to half open during climb out (he knew from
experience that worked about right). For descents he slowed the
airplane into the white arc and then descended with full flap and
a fair amount of power, staying in the white arc.

So, I don't have any magic answer, but keep ground ops and flying
separate. There's no comparison between a 140knot breeze flowing
past the cowling and propwash on the ground, IMHO.
Have a good holiday, rick