I have a dog barrier that I picked up off the internet somewhere, it's tension based but has suction cups at the top and bottom to disperse the pressure so it doesn't mar up your headliner. I don't use it anymore because I switched to a two crate set up and the fact that my 18 month old German Shorthair figured out just how to pull it down when I'm not in the car (he also knows how to open his crate from the inside). It's definitely solid, I'll probably sell it since I don't use it anymore, just have to find a box to put it in for shipping, PM me if you're interested and I'll try and get a pic of it in the 4R to give a better idea of how it looks.
I tried that one from PetSmart, and returned it because it had no top support, but didn't think of the pipe insulation to prevent marring at the time, nice idea.