Radiator drag

[camber]

Very Interesting!

One thing I am not sure of, does Hurri "Flap 6 notches open" correspond to fully open? It seems likely.

So converting to kmh, the Hurri is losing around 8kmh to the rads at a middle-low speed (340kmh)

The 109 is losing around 50kmh at a high speed (570kmh).

As form drag is very nonlinear with airspeed (supported by real data above) it would be fantastic to see this modelled. Poodling around with fully open rads would be fine, but it would be very detrimental trying to get fast. Good pilots would be having to perform rad adjustments.