In between other jobs I also mixed up a very small amount of tank sealant and glued a piec of fine mesh over the outlets of the two fuel tank vent fittings. The picture below shows how I did this. When fully set, in a day or so, then I'll trim the mesh back so it looks much neater.
Gluing fine mesh to the fuel vent outlets
Tank sealant - the worlds most stickiest, gooiest, gloop!