The Chung stuff works GREAT for comparing A to B. Not for determining the absolute values of A and B.
So, you can determine that helmet A is better than B by a CdA of .005. But you can't say your CdA with helmet A is .230 and with B it is .235.
Even adding in known live sensor wind vectors I don't think it is good enough to determine an absolute. Close, but close counts in horseshoes and hand grenades.
I'm going to kick tires locally among some triathletes with money to see if anyone wants to get together and do arena laps on the Chung method and swap helmets and swap equipment you're interested in buying someday.
I need to setup my Arduino Uno to a $25 pitot sensor and log the wind on test rides to get my Chung numbers even more reliable for equipment choices.
And buy a set of rollers to get good known CRR values to plug into the Chung models.