Correct on location. And I’ve read the rule book several times. To say it’s vague is understatement..
It just says a splash guard directing away from occupants and outside the vehicle. Probably build an air funnel or something to seal that extra cab window off from the back of the cab. Not trying to drive a couple hundred miles to get it banded and it not pass over something small like this.
hard pipe/tube from the filler through the firewall, full plate ext cab window filler. as mentioned get it as low as possible with a GIANT vent.
if it was mine, it would put it here

