Sending Unit Gasket Leak

[DUKE]

When I fill my gas tank to the top, gas leaks out through the sending unit gasket.
It is was installed without gasket cement, using the rubber gasket supplied only.
Stainless screws are self tappers directly into plastic tank, original threads are shot.
I know the easy answer is to not fill the tank, but I want to prevent water from leaking in also.
Suggestions? (see picture)