After a year or so of camping with the wife and 4 dogs, I decided to add a little more ventilation to my teardrop. I know the fantastic fans work well, but I don't know where all the expense goes in solving such a simple design, so here's what I did with some scrap 1/4" poplar.
I'll use computer case fans that I can flip to provide reversible air flow. If things don't go as planned, I can always shell out the big bucks for the fantastic fan.