No argument, just explaining my initial comment. As I said I did not explain it correctly, and I got the issues confused. So how can I be changing the goal posts when admitting I committed a foul? What you say is correct. However if the uniflow is off center the change is not as much because the pressure is reduced by the fuel above the pickup. The pressure at the pickup is always changing, but the pressure at the needle stays the same from full to empty.

Also the correct neutral (as far as pressure change from upright to inverted) position for a standard tank is for the centerline below the spraybar, it varies a bit because of tank size but it is always a small distance, 1/4" to 3/8" is common. But the neutral position for a uniflow tank is for the centerline of the tank to be even with the spray bar.