Hi there,
thank you all for the idea. I believe that a fire extinguisher is both a safety measure and a sporty mod. So I went for it, too. I riveted the housing on top of the beam behind the seats


It holds firm. Then placed a silver extinguisher I found online (it matches the rest of the interior)



And this is the final result. I quite like it, it gives the XF a tinge of extra sportiveness, don't you think?

Well then, let's set the road on fire. ;-)