Here is a new problem: I made some custom shoes using the correct method on a neutral base character, used the hide body mesh tool, and saved the shoes to the library. When I apply the shoes to a base character they fit correctly.

When I alter the base character with morph sliders, especially sliders that effect the hip width, the shoes no longer fit correctly. The shoes move away from center (see my attached sample). I can, of course, edit the mesh, select the shoes and slide them until they fit correctly, but this should work properly.