Well...
I don't know if you'd want to put the camera outside the car period...during a canyon drive. Too many things can fly around and hit the lens...and that would be a very bad thing.
The Hama suction cup should work on any non-porous surface inside and outside of the car including the paint (though I wouldn't put it there), but I can't see risking my expensive vid cams in that way.
I like putting the Hama mount on the rear glass (so I can see the dash) or the front windshield (to get nothing but road and a bit of hood). I bought Sony's 0.6x wide angle converter for my microMV vid cam, but haven't tried using it on the camera in the mount yet.