One of my Mopar manuals has a line about fuel line diameter and acceleration and it's totally wrong. I'm pretty sure they deleted it from later manuals. To reiterate: the pressure generated from accelerating a column of fluid is independent of the area of the column (or in this case, the diameter of the fuel line). The pressure generated is the product of the fluid density, acceleration rate, and the height/length of the fluid parallel to the direction of acceleration. Cross sectional area doesn't figure in at all. For instance, the pressure 50' below the surface of Lake Superior is the same as the pressure 50' below the surface of lake Huron, even though one has a much larger area. Let's put this myth out of its misery.
I'm not saying your wrong (because I can't find my fluids book)... But, I'm just thinking out loud here...
I think you're correct for a static condition, but doesn't the inertia from the weight of the entire fuel column come into play? Essentially if you think of the fuel in the fuel line as solid, the force generated back to the pump cavity (and thus the pump vane/motor) would be it's mass times horizonal acceleration. The larger the mass (Diameter), the more force is put on the pump vane to keep it all moving forward.
