Paper size (A4) problems

[lilypond]

Hi list,

I've been trying to something which I though would be simple with Lilypond: to
print music paper. Nothing took me too long to get done. Except for one
important detail: the size of the paper.

I've tried using set-paper-size on several sections of the Lilypond source, and
the result is always the same:

- The Postscript code generated seems to be larger than the pre-defined paper
size and appears clipped when viewed with a document viewer or when printed
(using Ghostscript). Of the 24 staves per page I expected, I see only 21!

- When looking at the generated postscript I see the following (I'm using A4
210x297 paper):
/page-height 307.289763779528 def
/page-width 217.275590551181 def

Now, I don't know what units are these, but they can't be milimeters, picas, or
anything related to the output-scale parameter...

What are these?
What can I do to have output of the correct size?

Bellow is the source code and part of the generated Postscript. Sorry about the
comments in portuguese.

Thank you,
Miguel Ramos


---- generated postscript snippet:
/lily-output-units 2.83464566929134 def %% millimeter
/staff-line-thickness 0.153766233766234 def
/line-width 196.582677165354 def
/paper-size (a4) def
/staff-height 4.0 def
/output-scale 0.966514459665145 def
/page-height 307.289763779528 def
/page-width 217.275590551181 def

---- the full source file:
% Miguel Ramos, Out/2007.
\version "2.10.29"

% Número de pautas por página.
staves = 24

% Tipo de papel e tamanho da pauta.
#(set-default-paper-size "a4")
#(set-global-staff-size 11)

\paper {
  %head-separation = 4\mm
  %foot-separation = 4\mm
  page-top-space = 6\mm

  ragged-last-bottom = ##f
  between-system-space = 4\mm
  between-system-padding = 4\mm
}
\header {
  % Elimina a etiqueta do Lilypond.
  tagline = ##f
}
\score {
  \new Staff {
    % Um espaçador de um compasso para cada pauta.
    \repeat unfold \staves { s1 \break \noPageBreak }
  }
  \layout {
    % Elimina o espaçamento especial para o primeiro sistema.
    indent = 0
    % No contexto partitura,
    \context { \Score
      % Elimina o gravador do número de compasso.
      \remove "Bar_number_engraver"
    }
    % No contexto pauta,
    \context { \Staff
      % Elimina o gravador da clave.
      \remove "Clef_engraver"
      % Elimina o gravador da indicação de compasso.
      \remove "Time_signature_engraver"
      % Elimina o gravador das barras de compasso.
      \remove "Bar_engraver"
      % Faz as linhas ficarem mais fininhas.
      \override StaffSymbol #'ledger-line-thickness = #'(0.2 . 0.02)
      % Extende a área de cada pauta um espaço para cima e para baixo.
      \override VerticalAxisGroup #'minimum-Y-extent = #'(-3 . 3)
    }
  }
}