Mount quad on camera

hi everyone,
here is alittle problem: i want to mount a quad to the camera, so it always stays
in place even if i move the camera around (and the rest of my scene). it already
works quite nice except for when i change the fov. i cannot figure out the right
ratio how to scale my mounted quad so it doesn’t move any more when i change the fov. it would be cool if anyone could solve this.

fixedquad.rar (16.4 kB)

use the node inverse transformation for your patch

fixedquad.rar (19.4 kB)