Shape note font failures

[Jim Duke]

I’m typesetting some A Capella music for congregational singing the uses the 7-note (Aiken) shape note system.  I’ve found that based on the system size some of the half note heads for RE (d in the example) are indistinguishable from quarter notes.  Basically the interior of the note head is filling in.  The following example reproduces the problem:

 

\version "2.18.2"

 

\score {

  \relative c' {

    \aikenHeads

    \override NoteHead.

    c2 d2 e2 f2 g2 a2 b2 c2

  }

  \layout {

    #(layout-set-staff-size 21)

  }

}

 

\score {

  \relative c' {

    \aikenHeads

    c2 d2 e2 f2 g2 a2 b2 c2

  }

  \layout {

    #(layout-set-staff-size 22)

  }

}

 

The D in the first system (at staff size 21) has the note head filled in.  The D in the second system (with staff size 22) has the note head hollow as it should be.

 

I’m not sure how to proceed with fixing this.  I can artificially enlarge the note heads; but that is an unsatisfactory fix that I’d like to avoid if possible.  I’m afraid the real fix would involve a change in the font definitions.  It seems the pen size is a bit too large.  Is there a way short of changing the font definition of controlling that?