I wouldn't argue with you about using SI units in professional
communications -- I do that all of the time -- but in this case I
started out with English units and it was easy to stay within them.
Also, and importantly, the question I asked was more easily understood
by most pilots here, and the more useful answers came back in the same
units. First rule of communication -- speak the language the spoken to
are most likely to understand!

my direct answer wasn't in another "language"; it was pretty straight, i
think. the formula i suggested is independent of units; so it can used also
if one calculates with imperial units.

you asked for an answer by "real engineers"; that's what you got.

i'm sorry if i confused anyone by giving additional information...