[andrearobinson]

I also never used the one I had in my last vehicle.

To quote myself from your other cargo cover thread:

I don't know how it is in the Passport, but I stopped using rear cargo covers years ago when I realized that my back windows were so dark that it was almost impossible to see inside anyway. The cover was just a hassle that often needed to be removed.

I'm a bit skeptical as to whether it would affect heating or AC very much - if at all.