merging the shaped note "fa"

[Eduardo Vieira]

Hello list,

I'm wondering if the problem with poliphony (voice overlay) with shaped notes 
have been solved in versions later than 2.7.17.
When the "fas" of two different voices (e.g. soprano and alto) are together, 
only one notehead should display.
Trying to do it manually by making one of the noteheads transparent (like I did 
in the 3 beat of the measure) just about solves the problem, except that the 
stem of the transparent note doesn't touch the corner of the other notehead.

Here is the test file:

\version "2.6.0"

\header {
 title = "The Fas"
}

staffPiano = \new PianoStaff {
 \set PianoStaff.midiInstrument = #"acoustic grand"
 \set PianoStaff.instrument = #"Piano  "
  \time 3/2
    <<
  \context Staff = "RH" {  % Right hand
    \clef treble
   \key c \major
   \set Staff.shapeNoteStyles = ##(do re mi fa #f la ti)
   \relative c' { < d f >2 << f2 \\ f2 >>
   
   << f2 \\  \once \override NoteHead #'transparent = ##t f2 >>
   }
  }
  \context Staff = "LH" {  % Left hand    
   \clef bass
   \key c \major
   \set Staff.shapeNoteStyles = ##(do re mi fa #f la ti)
   \relative c { < d f >2 << f2 \\ f2 >> 
   << \once \override NoteHead #'transparent = ##t f2 \\ f2 >>
   }
  }
 >>
}



\score {
 <<
  \staffPiano
 >>
 
 \midi {
 }

 \layout  {
 }
}

\paper {
}