Anybody care to speak about Line size for Feed vs Return?

Carbureted 440 6bbl. I have a Magna Fuel 285 picking up dual lines from welded in lower sump though #8. #8 Up to Aeromotive Regulator with #6 return.

I cannot get the Fuel pressure below 12 at the regulator.
This is bench testing before car has started.

I have since heard that the return must be equal or bigger than the feed.

Thoughts....Help???

1969 Hemi Charger R/T,
1970 Charger 472 Hemi 6 Sp
1969 Charger Pro Tour Project
1971 Barracuda Convert
1970 440 6pack Superbird,
1968 Fury I Police Pursuit 440 Super Commando 2 door sedan (Black/Blue)
1967 Barracuda Convert
1968 Barracuda Coupe
1972 Charger Rallye wanna be RT
1972 Sebring Plus 440-6 Clone
1969 Coronet Pro Street
2009 Challengeer SRT8 stick
1992-1986 Body 2500 4x4 440 stick
1982 Ramcharger 318 Sniper- getting enhanced.
1991.5 W250 Cummins- Big Chief