Triple 4k displays failed in window mode

I have three 4k displays and tried to show the game with 3 x (3840 x 2160) displays.

Because of some reason, I tried to use very wide(11520x2160) single window in windowed mode, with using of concatenated display by 3D Surround, nVidia.

Unity failed its initialization with such wide screen. I succeed to launch with 7680 x 2160 resolution. Is there any limitation of window size in unity?