Not sure why there is no setting to set the FOV to the desired value directly, but I can confirm that it works just as explained by the Racedepartment post.
my "best" FOV is 0.5x: as a 2013-member of r3e i only played with 1.0x. Since December 2017 i increased my FOV from 1.0 to 0.7... and holly cow... it's quicker an.... B E T T E R