The mounting screws that the fixture attaches to are about 14” too long. I had to buy new ones to be able to securely mount it. 
The mounting plate can only be installed one way, and the screws that attach to the fixture have heads that prevent it from laying flat against the wall because of my box configuration. The only way the mounting plate is secure is at the angle shown in the photo.
I installed and removed the fixture 4 times trying to make it work in its rigid setup and poor screw length.