Your right PKRWUD, brass does dissipate heat better, but some of the other elements in making those radiators (epoxy and such) do make them less effecient.
Anyway, if the car is staying cool at highway speeds, it's is obvious that for whatever reason he's not moving enough air through the radiator. But the Flex-a-lite fan he's using flows more than enought CFM, so where does that leave you?
If you go strictly by the flow numbers, the Ramcharger fan pulls 2340 CFM, the Flex-a-lite pulls 2500 CFM, and the Be-Cool/Spal fans pull a whopping 2780 CFM.
Again, I say to check the wiring on the fan.
