I know some very experienced fliers who won't put a filter between the tank and the engine on glow engines. Exactly because it is another potential source for an air leak. They convinced me to put the filters in the line you use to fill the tank, and that is what I have done for years.

Foreign material in the line will not introduce bubbles, just reduce flow. It has to be air entering between the clunk and the carb. Sometimes a bad seal at the needle valve stem, sometimes wear points in the lines at the tank fittings, sometimes bad seals of the metal tubes and fittings to hose. Sometimes vibration of the tank causes it to foam up (and the solution is to surround the tank with foam rubber).