[Ronbo]

Although most people don't do it I'd run an equal size return line as it's the opposite condition of the feed, at idle almost all the fuel the pump is delivering is being sent back to the tank by the regulator. If the return is too restrictive your idle pressure can climb above the set point of the regulator.

As most others have stated -8 (1/2), no point making the pump fight the line restriction. Not to mention over time the pump's output will degrade from wear.