> Customizing `hl-line-face' has no immediate effect. You must save the
> customization, quit Emacs, and restart Emacs, to see the effect.
Would the attached patch help?
Looking at it (without trying it), I'm not sure, but I suppose so.
However, please see my other email about using a face instead of a user
option (variable). Wouldn't that also take care of this problem? That is, if
there is no face variable, and users change the face itself, then that would
be immediately reflected in the overlay, no?