To operate BonyFace correctly your model needs to be:
  1. Editable Poly
  2. In the Front viewport, model has to be looking directly at you
  3. Scale has to be 100% at all axes. (Use Reset XForm)
  4. Separate objects for each eye, eyelashes, tongue, upper and lower teeth
  5. Local Z-axis of each eye has to be the line of view
  6. Directions of a local axes of each eye are almost the same
  7. Coordinates of all vertices of the head-model are Z-pozitive.
  8. Skin modifier (if it is present on model) has not to be empty (without rig).
  9. Skin modifier (if it is present on model) has not to be present on other objects.

The algorithm of automatic spline alignment is a most problem part of the script, if you got an error during it then close and re-open Adjust Splines window, skip the errored step and continue with next step. There is no undo, but you can always save positions of splines to bfs-file and re-apply them via Load Splines button in main window. Also you can adjust splines only by hands or by button of manual alignment. Remember that spline alignment is a 99% of whole work with rigging, others phases take much less time.
    Requirements to model, needed to the algorithm of automatic spline alignment works without errors
  1. Closed loops of eye edges and mouth edges (select single edge and press Loop button to check this):

  2. Model must have a central line of vertices (line of model symmetry):

  3. Vertices of horizontal line of the forehead and vertices of the line of symmetry must have 4 edges or less (Loop button have to select all of these edges)