Use what you have

[frater secessus]

A tank doesn't have to be full all the time.

[John61CT]

True also for big-a55 propane, but then the tank itself is heavier

[Motrukdriver]

The tank will be just behind the front seats more or less centered between the wheels. Empty when rolling and when I drop the TT to set up camp the wife and I can go grocery shopping and water tank filling. When we get back to the TT I'll use a transfer pump to move the water to a storage tank inside the trailer. I figure 100 gallons should last us about 2 weeks if we are stingy enough with water use. That is a smidge more than 3 1/2 gallon of water for each of us per day. I only shower twice a year even if I don't need one so there is a huge water savings right there.

[John61CT]

That's a very generous water allowance.

[TWIH]

Lots of minivans have excellent venting windows for outward flow.

Not that hard to rig inbound fans in closing vents through a spot in the floor, screened of course.

Not really, there are small back quarter glass windows that go out an inch or two, but allow rain in. Other than that, especially with rain, you are stuck. 

In the SW with the arid conditions that would be true though.

[Motrukdriver]

What ever is left over we'll use to clean what needs cleaning before we roll to the next camp spot or tell others to come and fill up their water jugs.

[John61CT]

but allow rain in.

I've used quite a few that didn't, especially with screens fitted, which of course you need.

Total square area of the opening is like having a regular window open all the way.