Lyric Entry

[Aaron Dalton]

I am brand new to Lilypond and am having a heck of a time getting lyrics to 
render properly.  I have 2 questions:

1) I want to line up the words "Agnus Dei" under a certain set of notes.  So 
far the only way I have been able to properly align the syllables "De-i" is 
using 3 dashes (see source below) but I only want it to display *one* dash in 
the center of the melisma.  If I enter "De -- i" or even "De -- -- -- i" it 
ignores the melisma.  Is there a way to make this only display one dash 
between De and i?

supMusic = \notes \relative f' { f2. c4 f8 g a2 g4 a2 r4 }
supWords = \lyrics { A -- gnus De - - - i, }

2) Second question is with position of the lyrics.  I have tried really hard 
to read the documentation and mailling list archives but have been unable to 
find my answer.  I copied and modified the satb.ly template to give myself 3 
staves.  The problem is, all my lyrics are printing above the staff and I 
want them below.  How do I do this?  Below is my actual source code.

Thank you so much for your time and patience!

\header {
 title = "Mass for Three Voices"
 composer = "William Byrd"
}

supMusic = \notes \relative f' { f2. c4 f8 g a2 g4 a2 r4 }
supWords = \lyrics { A -- gnus De - - - i, }

altusMusic = \notes  \relative c' { }
altusWords =\lyrics { }

bassMusic = \notes \relative c { }
bassWords = \lyrics {  }

\score {
 \notes <<
  \context Lyrics = superius { s1 }
  \context Staff = superius <<
   \set Staff.instrument = Superius
   \set Staff.instr = Sup
   \clef treble
   \time 4/4
   \key f \major
   \context Voice = superius \supMusic
  >> %superius staff
  \context Lyrics = altus { s1 }
  \context Staff = altus <<
   \set Staff.instrument = Altus
   \set Staff.instr = Alt
   \clef "treble_8"
   \time 4/4
   \key f \major
   \context Voice = altus \altusMusic
  >> %altus staff
  \context Lyrics = bassus { s1 }
  \context Staff = bassus <<
   \set Staff.instrument = Bassus
   \set Staff.instr = Bass
   \clef bass
   \time 4/4
   \key f \major
   \context Voice = bassus \bassMusic
  >> %bassus staff
  \context Lyrics = superius \lyricsto superius \supWords
  \context Lyrics = altus \lyricsto altus \altusWords
  \context Lyrics = bassus \lyricsto bassus \bassWords
 >> %notes

 \paper {
  \context {
   \VoiceContext
   \consists Ambitus_engraver
  }
 }

 \header { piece = "Agnus Dei" }

} %score

-- 
Aaron Dalton
http://aaron.daltons.ca