For all others reading this:
The aluminized reflective side is designed as a radiant barrier, which is only effective when facing an air space.
The "back side" of foam, either XPS or EPS, usually has a thin plastic sheet as a water barrier.
Which way you install the foam, to my knowledge, doesn't really matter in a teardrop camper, since both sides will be covered up, both sides have a water barrier, and there's no air space to allow the radiant barrier to work properly. So basically: You can't go wrong!
As far as your choice of headliner goes: Do you plan to install it with an adhesive or fasteners? That will really determine what sort of headliner would work best, I think.
