The extender kits usually use a standard outboard motor fuel tank. If you are concerned that the fuel line is too close to the running generator, simply disconnect and move away to fill it. If you do it quickly there will not be enough vacuum to shut it down. An alternative is to have two tanks and swap them out, they have quick disconnects.
One thing to watch is the surface of the generator gas tank opening. Those stupid government gas cans that have the push to fill can nick the surface and allow an air leak that prevents the draw from the remote tank.