Solutions for a slightly loose crown race
I was checking out Sheldon's website again and came across the following line in the article Servicing Bicycle Headsets:


  If the crown race is loose, sometimes you can fix it by using a hammer and centerpunch to create a series of "craters" in the side of the surface that locates the crown race. The raised edges of the craters may be just enough to remove the slop.


Although I was skeptical, this actually did the trick! I made punches 1/4" apart around the fork crown. Once I fitted the crown race again, there was no play at all.