I ran mine home today for lunch (5 miles), as was the purpose for building it and it did fine and not so much heat buildup.
Am going to afix a heat sink to the top and see if that helps.
On my 48 volt system, I didn't run the controller through the pot box snap switch and the car seemed to start smoother. I had solenoids on the pack + & - and lit the controller without the big contacter. The foot feed just brought the controller to life.
The 72 volt system has brought about a lot of changes.
Now when I step on the pedal, the contacter and all come on fast and the car has a lurch to it, that I don't like. Possibly driver practice will calm that down.