Good point and taken, suppose one differential being is that part / half of the radiator would at least have unfettered air and this is directly targeted at the hot area of the radiator. When fitting the EF Davies Craig made it implicit that the fan is as close to the inlet as possible for effective cooling.
The D2 already is designed for the heat of the Dual AC and if fitted we are replacing the advantage of having the rear cooled independently with the loss of the heater in front of the radiator. Certainly there is no energy for free, the loss of rear cooling is the cost of the energy.

