This should be the first mod on any camper. It is hugely popular on pop-ups since they have the side vents which don't promote very good air flow. I then got a TT with top vent and it was fine as long as temperatures were below 85. What I did was put 3 x 120MM computer fans on the top of the vent opening to draw air from down low.

It is on a switch and speed control. On those hot days, I flip the switch and run at full blast. This weekend it was 98 degrees out and no shade. It kept the fridge @ 30 degrees. I just replaced 2 of the cheaper fans this year. $26 from best buy and I was back in action. I put it on a speed control for when we are without power but I want a little air flow without maximum draw.