I have a full width GRS, with brand new radtec radiator, relatively new waterpump, 82 degree stat and fan switch, and see no overheating issues during normal driving at the height of summer.
However, it cant do a 20 minute track session in summer without getting out of hand, even with holes cut in the front bumper...

How are your fans mounted? between cooler and rad, or on the front of the cooler?