I'm curious to hear your findings. My dually sucks at a standstill on a hot day and it came factory with that pusher.
I took it out to see how it does. I set the fan so it goes on @40 MPH and continues to run for 20 seconds once it's told to shut off so, it won't start and stop rapidly when cruising ~40 MPH.
Anyway I drove around for a while, got it as super heated as I could in only 100° weather, pulled into my shop and let it idle for a while. The fan seems to help keep the engine a little cooler since it didn't go over 198° reading from the ECM. BTW the temp gauge reads around 10° hotter consistently.
It kept blowing cold air but, I didn't use a thermometer for before/after comparison. I'll think about doing it at a later date but, I'm happy with it so far