Sorry for raising the dead.
I guess I am still confused after reading this entire thread as to why a vortex generator would not help on an xA. The Airtabs are designed for trucks obviously and have a lot of testimonials and "independent" test results confirming that they work. The size of them when placed on a car seem to appear to my "untrained eye" that they would create more drag than necessary to be inefficient.
I beg to question, if the Airtab design was scaled down to work on a car such as my xA would it give us a noticeable result?