I have a window air condition unit to install but it is 6" to wide for the window. From top to bottom it is fine.

I have no problem with cutting out the space needed to accommodate the unit but am concerned with the support to hold it in. The location is a 2nd floor stairway landing.

To the right of this window is the hallway wall which I presume has a support coming down that corner but then question if it's okay to have a window air conditioner flush with an interior wall.

To the left of the window is the exterior wall by the staircase and I have no idea how far that way to the next support.

I'm pretty handy and with good instruction think I could complete the project but I need to be sure I'm doing it correctly. I don't want this 180lb monster to fall out and kill somebody!

Any instruction, tips or links to help are most appreciated.

Thanks in advance for your assistance.