centered chorus lyrics

[Little Lee]

I'm typesetting a piece of music that my mother wrote
that has two verses and a chorus.  I want the lyrics
to the chorus to be centered between the two staves,
but I can't figure out how to do that.  I can only get
the chorus lyrics to either line up with one of the
two verses, or to create a third line of lyrics.  Can
anyone help?

Here's a sample:

\version "2.8.5"

upperv = \relative c' {
        \clef treble
        \key g \major
    \time 4/4
    
                  d4 e8 d g g a g
                  c4 b g4. g8
                  a4. a8 a4 g8 a
        \break
                  c4 b a8 g4 d8           
        }

upperc = \relative c' {
                  e'4 e c e8 c
                  d4 c b2
                  c4 c a c
                  b8 c4. d4 g,            
        }

lowerv = \relative c {
        \clef bass
        \key g \major
        \time 4/4
        
                  <d g b>2 <d g b>
                  <c e g> <d g b>
                  <d fis a c> <d fis a c>
                  <c e g> <d g b>                
        }

lowerc = \relative c {

                  g4 <c e>2 <c e>4
                  g4 <b d>2 <b d>4
                  fis4 <c' d>2 <c d>4
                  g4 <b d>2 <b d>4 
        }

wordsOne = \lyricmode {
                  These are the words to the first verse.
                  la la la la la la la la la la la la la
        }

wordsTwo = \lyricmode {
                  These are the words to the second verse.
                  la la la la la la la la la la la la la
        }

chorus = \lyricmode {
                  These are the words to the chorus.
                  I want them to be centered. la la
        }

\score { 
  <<
        \context Staff {
                \context Voice = upperv { \upperv }
                \context Voice = upperc { \upperc } 
                }
        \lyricsto upperv \new Lyrics \wordsOne
        \lyricsto upperv \new Lyrics \wordsTwo
        \lyricsto upperc \new Lyrics \chorus
        \context Staff = lower { \lowerv \lowerc }
  >>
}




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