PJ2; I agree with your statement, but by using an accurate device and having also checked other formulas.
I use the 5kt/1000ft or 2%KIAS *1000ft rule which although a bit inaccurate for these cases, they serve me well for more general cases involving higher flight levels.
Be aware though that having checked with a CR-2 and other formulas ( a good one which does it all for you;
http://www.paragonair.com/public/aircraft/calc_TAS.html
isnt always accurate, as I have calculated in both ways for another case:
Say at FL 390, M.78,240KIAS,-56º, QNE. using that formula which someone else I think used before it comes out to 473KTAS. Using the 5kt*1000ft rule comes out to KTAS435kts, and the 2% of KIAS to even less. Well the real good answer is a near KTAS of 450, and that is with a B738 plane.
Then again its all a bit unprecise, In this case I would trust more in what someone who flies quite alot there has to say about the TAS on final app.
Regarding RWY 35 used with tailwind, as polea said bfore, It could be because its the only one with an ILS.
BlueFalcon.