Merritt, thanks for the clarification. You're right, I didn't realize that the Trekker lacks the radiant barrier. It has the layers of film, like the other Neoair pads, but the film isn't aluminized.
I see your reasoning now. Yes, some IR from your body probably gets through the Trekker to the ground, so substituting a space blanket for some other film-type groundsheet might help a little.