Problem with borderless fullscreen in multimonitor configuration

I use 2 monitors with native resolution 1920x1080 each. Videocard is GeForce GTX 660, and video driver version 372.70. OS Windows 7 x64.

For some reasons I need to use custom resolution 1280x900 on my secondary monitor. I create custom resolution in nvidia control panel. In choose new resolution in path of exile options and fullscreen settings and everything works fine, but when i change settings to borderless fullscreen game become 1920x1080 and of course not fit inside custom resolution, part of game cropped. I am not sure, game take settings from primary monitor with this resolution or somehow read native monitor resolution of secondary monitor.