Fuel restriction w/ 6an line?

All of you are sort of correct. Pressure will "try" to drop under HIGH flow conditions downstream of the regulator, and if the flow is high enough, and if the tube is small enough, pressure WILL drop

Static pressure is not affected by tube size

However, unless this is a 600hp monster and or running E85, I doubt that no6 would be an issue. Hell there were some pretty impressive old-school cars ran on 5/16 line all the way from the front to the rear.........which brings up another issue...........

and that is that tube size pressure drop depends on pressure IE pressure drop is much more severe as the line LENGTHENS, and is much worse on the inlet (lower pressure) side of the pump