spacing between staves

[Marc Hohl]

Hello all,

after reading the manual and the archives, I have to admit that I am
probably too stupid for the new spacing system.

I have the following song template and I want the staves to be further apart
so they fill about 2/3 of the entire page.

I fiddled around with ridiculously high values for padding, 
basic-distance and minimum-distance,
but the staves don't move.
Most probably, I overlooked something or misunderstood the manuals 
completely.
Any hints would be highly apprechiated.

TIA

Marc

\version "2.13.48"

\paper {
  indent = 0
}

\header {
  title = "test"
  composer = "me"
}

\layout {
  \context {
    \Staff
    \override VerticalAxisGroup #'staff-staff-spacing =
    #'((basic-distance . 8)
         (minimum-distance . 7)
         (padding . 1))
  }
}
words = \lyricmode { this is just plain text }

mychords = \chordmode { c1 | c | c | c | c }

melody = \relative c' {
  c1 | \break
  c | \break
  c | \break
  c | \break
  c
}

\score {
<<
  \new ChordNames \mychords
  \new Staff {
    \new Voice { \melody }
    \addlyrics \words
  }
>>
}