Cpt.....
To get it right I think you need to empty the tank as much as possible, adjust the empty mark, then fill to full and again adjust to your mark. Kind of a compromise.
How ever I don't see why filling and adjusting, then driving until it is low and making the final adjustment to the empty mark wouldn't work?
PS...I'm still at my Daughters (Columbus) using the marvelous laptop---Son N Law added a connection to his router.....My gawwsh
this thing is great!!!