I think the Cd 0.212 reported for the Tatra will be one of those numbers Hucho warns us about.
The Tatra 87 was measured in a modern wind tunnel and scored Cd 0.36,much higher than published in the late 1930s.
PS All the Tatras must be envisioned without their stabilizing rear fins,which from the side,confuse the actual roofline of the cars.