OK, before fast coolers, I ran more less 100*F (cooler ambient temps) to 135*F (higher ambient temps) unloaded. I have since added coolers and while I have only had it to 90*F Ambients, but it seems to run under 100*F above ambient temps (or in other words at 90*F, it runs around 185*F)... and this was towing a small trailer and a 1500 slide in camper in the back.
I also found that with my NV5600, overfilling by a quart (before adding the coolers) caused the transmission to run hotter (with the same fluid used in the previous fill)... so I am not convinced that is such a good idea and I am not running overfilled with the FastCoolers like they suggest.
The hottest temp I ever reached without coolers was 235*F.
steved