chord/rhythm/melody staves: putting it all together

[lilypond]

Thanks again to those who helped with earlier questions.

This example snippet of some simple changes with implied rhythms
and complex changes with explicit rhythms looks great.  The vertical
spacing of the chords and rhythm marks is tight but still legible:

\version "2.14.2"

SimpleChanges = \chordmode { g2:m f }
SimpleMelody  = \relative c'' { g4 c a f }

ComplexChanges = \chordmode { g4:7 g:m7 f:maj7 f8:7 d8:m7 ~ d1:m7 }
ComplexRhythms = { g4 g f f8 d8 ~ d1 }
ComplexMelody  = \relative c'' { g4 c a f ~ f1 }

\score {
<<

% ChordNames staff begins here.
  \new ChordNames {
    \key f \major
    \repeat unfold 2 \SimpleChanges
    << \new RhythmicStaff \with {
         \override NoteHead #'style = #'slash
         \override StaffSymbol #'line-count = #0
         \override StaffSymbol #'staff-space = #(magstep -3)
         \override BarLine #'stencil = ##f
         \override TimeSignature #'stencil = ##f
         \override KeySignature #'stencil = ##f
         \override Clef #'stencil = ##f
         explicitKeySignatureVisibility = #end-of-line-invisible
       } {
         \key f \major
         \set fontSize = #-5
         \ComplexRhythms
       } % end rhythmic staff
       \ComplexChanges
    >> % end of complex rhythm section
%    \MoreSimpleChanges could go here
  } % end of ChordNames block

% A melody staff (simultaneous to the chord staff) begins here
%  \new Staff {
%      \repeat unfold 2 \SimpleMelody
%      \ComplexMelody
%%    \MoreSimpleMelody could go here
%  } % end of melody staff
>>
}

Now I'm ready to add the melody staff at the bottom.

But when I uncomment the melody section, the melody staff gets
inserted not at the bottom, but in the middle.  The entire
ChordNames block is closed before the the melody staff is added
to the score.  Why does the newly added melody staff 'split' the
ChordNames section?  How do I tell Lily to put the Melody staff
below the ChordNames block, rather than in the middle of it?

Also, the 'ComplexRhythm' section seems redundant.  I have
already specified those rhythms in the ComplexChanges section.
But if I reference \ComplexChanges as the music for the rhythm
marks, I get multiple noteheads on the rhythm stems.  I presume
this is because the ComplexChanges contains chords, which of
course are polyphonic.  Some notes are engraved left of the stem,
others to the right of the stem, so most all of the chords get
pitch-squashed down to one left-note and one right-note.  Is
there a way I can tell the RhythmicStaff section to squash each
chord to a single note, so that just the rhythmic content of the
ComplexChanges music is used for the rhythm marks?


Thank you!


Jim