Where can you find a 4 core aluminum for our trucks? Never seen a single one...if there were stock ones that bolted in, I'd be all over that. (when mine fails)
I have a feeling, and no conclusive proof, that if the pusher fan and puller fan speeds are not exactly the same, one will be restricting the other. I don't *personally* think pusher fans are a good idea if you can get by with adequate puller fans.
Flexfans are horrible. (if we are talking solid bladed and no clutch) Even if they don't throw a blade through your hood, or eat into the radiator at a water crossing, the unnecessary power drain and impedement of air flow at higher vehicle speeds make them pointless for use. Yes they are lighter than a clutch fan, and probably tend to increase consistency if racing (consistent drag on the engine, not on/off like a clutch fan) but either of those don't mean much on a daily driver, or a vehicle that spends a lot of time at low engtine RPM's.
I know flex fans work in some cases, but IMO, its not the flex fan that is doing such a great job, its the attention that has been lavished on the entire cooling system that is rewarded, the flex fan just happens to be along for the ride /forums/images/icons/wink.gif
Totally off the fan topic here, (back to overheating in general) but aren't rapid engine temp changes associated with how much throttle is being given, sometimes attributed to bad head gaskets??