ive spent the last 16 hours or so just playing around with mode 7 and im pretty certain you cannot CHANGE the fov. you can change the rotation angle. but thats just the direction the fov is faceing.
the field of view is usually a wide angle related to the directional angle.
on a 60 degree FOV
if youre facing 0 degrees your fov is from 0 - 30 degrees to 0 + 30 degrees between 330(-30) to 30
im just uncertain what the actual fov in the mode 7 ex object is. i know its pretty close to 60 but not exactly.