These pics shows the internal baffle construction found inside of Model A cowl gas tanks. Note that it is near impossible to effectively reach all areas of the tank for cleaning through the openings. It would also be difficult to insure coverage of all the surfaces with a tank sealing compound.
Sometimes the spot welds on the baffles break due to fatigue from fuel sloshing, and this can cause an annoying rattle inside the gas tank.
Also seen is the shape of the gas tank in the areas behind the external brackets.