TCR uses a wind tunnel for aerodynamuc testing, and that's for over a dozen different models.
"The homologation process [of the MG6 TCR] included engine tests on the dynamometer bench at ORAL Engineering and
aerodynamics tests in the Pininfarina wind tunnel"
https://www.tcr-series.com/news/item...on-formalities
Why Supercars are unable to do it for just two models defies belief!