Two problems with the Porsche 3rd radiator, first it's an oil cooling radiator for auto-trans cars, not specific for water. I installed a custom 3rd radiator and used the same mounting points. In the last year I installed a 997 GT2 after market bumper that has the gill vents in the top of the bumper and at the same time I leaned the top of the radiator forward so now I get a flow of air through the radiator.
With all of this I saw some improvements in 90-100 plus degrees driving 75 MPH with the A/C on.
