In-game, make save-point (play or change settings), quit. Edit %USERPROFILE%\Documents\My Games\insane2\user_config.cfg. r_fullscreen "0", r_heigth & r_width your base PLP resolution. ShiftWindow (must Grab co-ords from game window, then edit Top offset until proper borderless. Bit odd, but perfect spread.)
(PLP screenshot with bezel effect)