depends if you drive in traffic alot. if you dont do to much heavy stop start traffic just use one thermo just means the aircon isnt very cold at idle. or change water pump and use fan. two thermos covering the radiator will cause lots of pressure once your driving air in over the speed of the fans. just depends on how hard you are going to drive. me i would bin the aircon evapretive and make way for better intercooler with greater cooling for it and the radiator.
mick