Get Steam VR camera viewport rect

Hello All!
I'm having an issue with Steam Vr camera viewport rect: it seems like steam Vr is overwriting it (on the Camera_Eye object) but I can't find where.

I need to make a camera render as the Camera_Eye (same viewport/ same FoV), but since I can't find the Camera_eye viewport rect (it stays 1:1 in the inspector), I can't do what I want ...

Any idea where I can find it ? Or the place where it is overwritten ?

Thanks !