I have a couple of Fantastic Fans. I can open one with no fan and use the second one to pull the air through and out. Nice to have.
Short answer is they are worth the money, but in triple digit weather pulling/circulating that heat really does not help cool anything.
Why not run one in reverse and really move air?
We decided against having air conditioning (for now) and instead installed two Maxxair Deluxe fans. We put them in the emergency exit roof hatches. They're low profile, can be set by thermostat (good for our bulldog) and have many speed settings. Plus, they're very quiet. The maxxair design does great when it's raining.The fans manage to pull a lot of air through the bus. Even with just one on the cooling effect is very noticeable.