I don't know if the there is an adjustment trim pot or not. .
Bend the float arm. Of course this will change the gauge calibration a bit too, but if you want to fool yourself that the tank is emtpy when it isn't, go for it. (Kind of like setting your watch 5 minutes fast IMO, if you know it's fast what's the point?).
Dave S
DMC Midwest - retired but helping
Greenville SC