After a few hours of use, the slight vignetting on your PB180 is actually exceptionally good. Many PB170 active matrix displays (I'm not sure if the PB180 has the same display) get this effect after a few minutes of use, to a much greater degree (almost like looking through a tunnel).

As the capacitor replacement in these displays is still not a confirmed fix in my mind, I wouldn't do any repairs at all at this stage.