Sorry to bump up this old thread but I'm currently facing this situation after removing a window aircon after upgraded to a split system. I'm thinking a simple fix is to get a piece of white acrylic and mount over the wooden corner on the aircon hole. This way, I can also allow sunlight to come into the room. Any comments if I do this?
Please PM me the info. Thinking of installing a system 3 non-invertor, looking at Panasonic, Toshiba or Mitsubishi. My bro's flat might need it as well.