Advice sought on making parts for string quartet

[Andrew Bernard]

I'm seeking the advice of the list expertise on the topic of producing parts for a string quartet. I think I know the answer to this in advance, but I want to validate my ideas. In the score I am setting for a composer colleague, we are fussy about pagination and line breaks. Lilypond does a marvellous job of layout out music, but all our scores use explicit page and line breaks at all times. I don't currently use a separate part to control the layout vis a vis line and page breaking, since the time signature changes multiple times per pages and it would be a major headache, two hundred pages of trying to track that separately.

The issue is that if I use tags to produce a score and parts as per the standard examples, the explicitly written page breaks cause the parts to have page breaks after each line, obviously, instead of line breaks.

I cannot be the only person to need to deal with this. What's the best practice for making parts when using explicit page breaking?

Do I have to have a separate part for breaking, and one to be used for the score, and one to be used for parts?

Andrew

In the interests of having an MWE that shows what not to do, i.e., my effort so far, here we are:

%====

%%file: score.ly

\version "2.19.82"

\include "piece.ly"

#(set-global-staff-size 14)

\book {
 
  \score {
    \new StaffGroup \keepWithTag #'score \music
    \layout { }
    %\midi { }
  }
}

\book {
  \bookOutputName "violinone"
  \score {
    \keepWithTag #'vn1 \music
    \layout { }
  }
}

\book {
  \bookOutputName "violintwo"
  \score {
    \keepWithTag #'vn2 \music
    \layout { }
  }
}

\book {
  \bookOutputName "viola"
  \score {
    \keepWithTag #'vla \music
    \layout { }
  }
}

\book {
  \bookOutputName "cello"
  \score {
    \keepWithTag #'vlc \music
    \layout { }
  }
}

%-----

%% file: piece.ly

\version "2.19.82"

Violinone = \new Voice {
  \relative c'' {
    c2 d e1
    \pageBreak
    c2 d e1
    \pageBreak
    c2 d e1

    \bar "|."
  }
}

Violintwo = \new Voice {
  \relative c'' {
    g2 f e1
    \pageBreak
    g2 f e1
    \pageBreak
    g2 f e1

    \bar "|."
  }
}

Viola = \new Voice {
  \relative c' {
    \clef alto
    e2 d c1
    \pageBreak
    e2 d c1
    \pageBreak
    e2 d c1
    \bar "|."
  }
}

Cello = \new Voice {
  \relative c' {
    \clef bass
    c2 b a1
    \pageBreak
    c2 b a1
    \pageBreak
    c2 b a1
    \bar "|."
  }
}

global = {
  \time 4/4
  \key c \major
}

music = {
  <<
    \tag #'score \tag #'vn1
    \new Staff \with { instrumentName = "Violin 1" }
    << \global \Violinone >>

    \tag #'score \tag #'vn2
    \new Staff \with { instrumentName = "Violin 2" }
    << \global \Violintwo>>

    \tag #'score \tag #'vla
    \new Staff \with { instrumentName = "Viola" }
    << \global \Viola>>

    \tag #'score \tag #'vlc
    \new Staff \with { instrumentName = "Cello" }
    << \global \Cello >>
  >>
}

%====