Nearly cooked four nucs moving them in an enclosed trailer — ventilation lessons the hard way

Confession time so nobody repeats this. Moved four 5-frame nucs about 90 minutes to an outyard on Tuesday. Screened their entrances shut, loaded them in my enclosed cargo trailer around 9am, figured the trailer shade would keep them cooler than the open truck bed. It did not. Hit stop-and-go traffic, no airflow, and when I opened the trailer two of the nucs had bees pouring sweat — clusters broken down, bees fanning frantically at the screens, one had started to slump a patch of new comb. Got lucky: soaked them with a water mist, drove the last leg with the doors bungeed half open, and everyone survived. A commercial guy told me after that closed box trucks kill more bees than winter does. What's the right setup? Screened tops instead of just screened entrances? Night moves only? AC?