My first suggestion to you would be advice on the roof vent fan - I'd strongly recommend you check out the MaxxAir product:
MaxxFan
Key feature is the rain shield is integral to the unit - allowing you to have have it open and
actually use it during inclement weather (in addition to having it open while you drive) - as opposed to just buying a product that will close itself when it starts raining.
I'd also suggest getting the motorized model with the handheld remote control - I wish I had - mine is all manual meaning I have to have to open or close it by hand when I want to ..... usually that isn't a problem ...... unless I have tall skid loaded and then reaching it can be a problem
If I had the remote, then all I would to do is hit a button and the motor would open or close the vent - and I could control the fan speed, the temperature that it comes on at, and whether it's blowing in or out remotely as well. As it is now, the only thing I can do with the model I have, is turn it on or off from the front of the vehicle.
BTW, my best cooling results are with the fan blowing in and the front windows cracked about an inch or so for exhaust vents - this seems to cool off the interior better. If I do the reverse of that, I can lie in the bunk and hold up my hand and feel the cool air being pulled across the ceiling ..... and out the vent ...... while I lie there sweating below .......