Game spreads perfect & is native borderless.

(PLP screenshot with bezel effect)

(1080p comparison)
Shortcut/launcher argument -popupwindow. In-game windowed. ShiftWindow (fullscreen resolution & to position).


(1080p comparison)
NOTES:
1. In-game FOV slider (not needed, untested).
2. Negligible oddities:
A. Appears bit brighter than single-screen, because game's black-gradient overlay is stretched full.
B. If FOV is left default, game is very slightly FOV+.
View guide for general help with the instructions.