I've yet to see any published data that actually measures efficiency, regardless of the number of rows or type of charge cooler.
Airflow and temperature difference and water flow and temperature difference are needed to calculate efficiency.
That said, the efficiency of a core is pretty much useless in practical terms.
For short duration use, the only thing that matters is the effectiveness of the system. For that, a measure of ambient inlet air temp, compressor outlet temp, and charge cooler outlet temp, all at various pressures and flows is needed. Cooling medium properties really don't matter.
If it is to be used in a true, steady state application, then the ability to reject heat in the cooling medium comes into play as well.
Using "efficiency" numbers as provided by a core supplier / manufacturer pretty much mean nothing. The engine doesn't "care" about anything but the amount of oxygen and the temperature it gets.