Yes you're thinking is spot on... adding extra obstacles to the air flow through the radiator will inherently lead to raised peak temperatures, I suppose the best setup with the engine's cooling made a priority would be no oil coolers OR A/C condensers directly placed in the airflow's path towards the radiator... life without A/C in summer would be a little tough though eh?
EDIT: Aluminium has a lower thermal conductivity efficiency than copper, generally popular as a weight saving alternative... what is the CFM rating of those 3 thermo-fans you've got fitted?