Thiel owners please chime in.

Your mileage may vary but doesn't hurt to try. Yes please report back. I'll chime in more after extended listening.  

Don't know about 2.7's, but both my 2 2's sound better on the 8 ohm than the 4 ohm.  Why, don't know given the impedance curve, although it does rise in the midrange/treble a bit.

After listening for a few days I have found the same thing, on my Mcintosh 501’s the 8 ohm tap sounds better, smoother, than my 4 ohm tap with my CS6.

I never would have guessed with the impedance staying below 4 ohms throughout the frequency range, I am assuming the CS6’s negative phase angle helps the low impendace load.  It is above my head, I just know what I hear.

From what Roger Majeski of Music Reference, and others have advised me, choosing the technically correct tap only maximizes the efficiency of signal transfer from amp to speaker. So the speakers can get louder when the "correct"tap is chosen. But, for nest sound, the way to do it is ONLY by listening, and deciding for yourself. --Warren