[Shadofax]

That cavity sure looks like the cap should fit in, but IMHO it doesn't fit securely. I did have it fall out once. It hit the fender causing no damage. But that was enough. I simply found it a lot quicker and more fool proof to hang it down. I do the same thing on my 997 (2010 911).

Same here, it has that little stand up ear, I just take the plastic line and put it behind that and let it hang.