fuel tank selector valve

[slug]

ok guys, i have a 83 chevy with dual tanks. i just installed a electric fuel pump and regulator and im haveing a problem with the fuel pump building to much presure and flooding out the carb, even with the regulator at its lowest setting. so, i ordered a new regulator with a by-pass that will bleed off excess pressure and send the excess fuel back to the tanks. my question is, on the fuel tank selector valve there are 6 ports on it. 3ea. 3/8" fuel line ports (2 into the valve and one out) and 3 smaller 5/16"(im guessing vaper return lines). im wondering if it would be ok to use the vapor return lines (5/16") as fuel return lines.