Ok, probably didn't explain it quite well enough.

3 Lines go through the tank

Line 1 - "Clunk line".
On the inside of the tank is a Felt Clunk (very low price from the local saw shop), attached to a piece of flexible gas safe line (Tygon, Viton or similar such material - NEVER silicon Glow fuel tubing). On the outside is a line going directly to the carb.

Line 2 - "Fill Line"
On the inside of the tank this line goes to the bottom of the tank. (When using a Dubro style stopper as listed in the OP, I use a solid piece of metal tubing with a 90 degree bend for this). On the outside of the tank is a flexible fuel line that goes to the Fuel dot (or in the case listed by the OP, the fueller valve). Some like to have a filter in this line, I have never found it necessary.

Line 3 - "Vent Line"
On the inside of the tank is a line that goes to the top of the tank. (When using a Dubro style stopper as listed in the OP, I use a solid piece of metal tubing with about a 45 degree bend for this and with a small piece of flexible line on the end - usually cut with a "V" on the end - it sits right at the top of the tank). On the outside of the tank, is a flexible line that goes above the eank then exits below the tank through the fuselage. (I usually glue on a piece of balsa at the bottom of the firewall and run the end of the vent through that to hold it in place.)

On my fuel filler tank, I filter the fuel going into it through a fine filter and I have a paper filter on the outlet of the filler pump to ensure the fuel going into the plane is clean. The felt clunk takes care of anything that may get past this.

I don't add anything to the line from the clunk to the carb as I have seen too many problems over the years where tee's etc in this line have caused air leaks. (The gasser carbs have a pretty effective pump in them and if there is a pinhole to be found, they will find it and suck air through it even if it isn't large enough for fuel to leak out).

I will try to find some photos of one later if nobody else manages to post it before then.