}In heavy traffic I slow down a bit, mostly so I have more buffer zone in
}front to balance the minimal buffer behind, but I also often find that the 
}jerk behind will notice traffic moving faster in other lanes, switch
}into one of them, and pass me - which is fine, because then I can keep a
}better eye on the jerk from behind, while looking ahead, rather than
}from in front, while splitting my attention between ahead and the mirrors.

This is pretty damned complicated. I just make a "back off" motion with
my hand/arm, and the second or third time even the most braindead cager
backs off. If they don't back off then, I find a way to get the hell out
of there -- the cager is either psychotic, drunk, or just a complete
asshole. In any case, I don't want to be anywhere near, and especially
not in front.