Foam is there to control slosh, you have a sump
but dont have any baffles.... it MIGHT slosh enough
to suck air in a low fuel condition. If you go with
a larger return line(larger than the supply) you know
you wont ever have a pressure build up in the return
causing the regulator to act goofy. I'm not sure about
the bulkhead fitting. The coil of line is for expansion
in the tank, it will break a suction if one were to
develop