Three more questions: centered instr. names / neomensural noteheads / incipit

[Amélie Aubut]

My sheet of music would be Perfect:

1) If I could get the instrument names (Superius, Contratenor, etc...) to be 
centered, instead of being right-align as they are righ now.   I tried to 
do:
\set Staff.instrument = \markup{ \right-align "Superius"}
for each instrument name, but it did not work properly, it gave quite of an 
anarchic alignment...

2)  If the modern clefs were right beside the double bar (instead of beeing 
apart from it).  I guess this as something to do with the skips needed so 
that the new clefs get printed after the double bar, but I can't see what I 
can do to get rid of that huge space between the incipit and the main 
body...

3)  If, in the Incipit, the stems of neomensural note were centered with the 
note heads.  In Lilypond's user manual, here,
http://lilypond.org/doc/v2.8/Documentation/user/lilypond/Ancient-note-heads.html#Ancient-note-heads
it is said that "The neomensural style differs from the baroque style in 
that it uses rhomboidal heads for whole notes and all smaller durations. 
Stems are centered on the note heads."  An exemple is given, for neomensural 
style, but the stems are NOT centered on the note heads.  I think it is a 
bug...   Is there a way I can center them manually?

Here is my sourcecode:


\version "2.8.5"

global = {

 \set Score.skipBars = ##t
#(set-accidental-style 'forget)

 \key c \major
 \time 2/2

 \override Staff.SystemStartBracket #'transparent = ##t
 \override NoteHead #'style = #'neomensural
 \override Voice.Rest #'style = #'neomensural
 \set Staff.printKeyCancellation = ##f
 \cadenzaOn
 \skip 1*1   \bar "||"  \skip 1*1   \bar ""

 \override Staff.BarLine #'transparent = ##f
 \revert Score.SpacingSpanner #'spacing-increment
 \cadenzaOff
 \once \override Staff.Clef #'full-size-change = ##t
 \set Staff.forceClef = ##t
 \key c \major
 \time 2/2
 \override Voice.NoteHead #'style = #'default
 \override Voice.Rest #'style = #'default
 \revert Score.SpacingSpanner #'spacing-increment

 \skip 1*1
 \set Staff.printKeyCancellation = ##t
 \set Staff.forceClef = ##f
 \override Staff.SystemStartBracket #'transparent = ##f

}

discantusNotes = \relative g' {

   \set Staff.instrument = "SUPERIUS"

        \clef soprano
        g4 c c b8\( c\) \noBeam
        \skip 1*1 % one bar

        \clef "treble"

        \cadenzaOn
        g4 c c b8 c d4 c4.\( b8\) \noBeam a8 b
        \cadenzaOff
        \bar "|" \break

}

discantusLyrics = \lyricmode {
        _ _ _ _ _
         \set stanza = "1. "
        Des sus l'her -- be __ _ fleu -- ri -- _ e,   __ _     }

altusNotes = \relative g' {

   \set Staff.instrument = "CONTRATENOR"

         \clef alto
        d4 f e g
        \skip 1*1

        \clef "treble"

        \cadenzaOn
        d4 f e g g e2 f4
         \cadenzaOff
         \bar "|"      }

altusLyrics = \lyricmode {

        _ _ _ _
        \set stanza = "1. "
        Des sus l'her -- be fleu -- ri -- e,    }

tenorNotes = \relative g {

   \set Staff.instrument = "TENOR"

       \clef tenor
        b4 a c d
        \skip 1*1

        \clef "treble_8"
        \cadenzaOn
        b4 a c d b c2 c4
        \cadenzaOff
        \bar "|"
}

tenorLyrics = \lyricmode {

        _ _ _ _
        \set stanza = "1. "

        Des sus l'her -- be fleu -- ri -- e, }

bassusNotes = \relative g {

   \set Staff.instrument = "BASSUS"

         \clef "petrucci-f"
         g4 f a g
         \skip 1*1 % one bar

         \clef "bass"
         \cadenzaOn
         g f a g g, c2 f,4
        \cadenzaOff
        \bar "|"
}

bassusLyrics = \lyricmode {

        _ _ _ _
        \set stanza = "1. "
        Des sus l'her -- be fleu -- ri -- e,  }


\book {

\score {


 \new  StaffGroup <<
   \new Voice =
     "discantusNotes" << \global \discantusNotes >>
   \new Lyrics =
     "discantusLyrics" \lyricsto discantusNotes { \discantusLyrics }
   \new Voice =
     "altusNotes" << \global \altusNotes >>
   \new Lyrics =
     "altusLyrics" \lyricsto altusNotes { \altusLyrics }
   \new Voice =
     "tenorNotes" << \global \tenorNotes >>
   \new Lyrics =
     "tenorLyrics" \lyricsto tenorNotes { \tenorLyrics }
   \new Voice =
     "bassusNotes" << \global \bassusNotes >>
   \new Lyrics =
     "bassusLyrics" \lyricsto bassusNotes { \bassusLyrics }
 >>

 \layout {
indent = 4.0\cm                     }    }     }



Thank you in advance for your help :-)
Amélie Aubut