Hi Curt,
FWIW; Hope this helps a little to partly analyze the vintage Model A fuel filtering system.
Tops of vintage vehicle glass bowls provided in such a fuel filtering systems have a lower inner, round glass step for the non-ferrous fine mesh filter screen to rest on; & also an outer higher sealing round glass step for the cork or rubber gasket to rest on & to seal the top of the glass bowl after this gasket has been compressed with the lower threaded connection.
Fuel enters the glass bowl by gravity, through the center hole of the filter screen and/or through the center hole of the 3039 paper filter element; hence, larger rust particles & fuel debris falls to the bottom of the glass bowl or with a 3039, falls to the metal bottom of the 3039 fuel filter by gravity.
Fuel next flows by head pressure upwards & out of the forward positioned gas line & then flows by gravity down to the carburetor ......... with only the original horizontal screen, this fine screen filters the fuel ........ with a 3039, the vertically provided pleated paper filters the fuel.
The 3039 filter has an upper, horizontal paper disc with a center hole, similar to the center hole in the screen, & the 3039 also has outer drilled holes inside the outer circumference of the disc to allow passage of fuel upwards & out to the carburetor.
The cork or rubber glass bowl gasket compresses when tightened, & pushes down inward on both the screen & the 3039 top circular paper element to seal & prevent fuel from passing through the outer edges of these filters.
If a 3039 filter is installed, the fuel debris will remain inside the 3039 pleated paper filter.
The original non-ferrous screen could be omitted when the 3039 is in use; however, I install the screen on top, just in case there is a one-in-a-billion chance that the paper filter would come unglued or get clogged, where it could be discarded & thus allow the original screen to continue filter fuel in an emergency.
The vintage screen mesh is also fine enough where water will not pass through it -- if one gets fuel with water, one can see the water resting in the bottom of the glass bowl.
Others may be able to add more.
-- I use ONLY the old cast iron type bowel, has a good fool proof screen, never leaks, nothing to look at & wurry some more
Wurry is non-productive, it's jist playing tapes in yo' head thet says,"WHAT IF"-WHAT IF?-WHAT IF?-----------& WHAT IF, usually NEVER happens, anyhow! Concern is a better alternative!