sustainOff moved horizontally

[Robert Garrigos]

Hi,

I want to move a \sustainOff horizontally but cannot find the way:

%%%
\score {
  <<
    \new PianoStaff
    <<
      \new Staff = "upper" \relative c' {
        \key ef \major
        \time 4/4
        <<
          \new Voice {
            \voiceOne <bf g'>2( ef4. bf8)
          }
          \\
          \new Voice{
            \voiceTwo g2. r4
          }
        >>
      }
      \new Staff = "lower" \relative c' {
        \key ef \major
        \time 4/4
        \clef bass
        ef,,8(\sustainOn bf' ef g bf ef g4)
        % \once \override SustainPedal.X-offset = 1
        \sustainOff
      }
    >>
  >>
}
%%%

this prints:

but I want the sustainOff symbol right under de bf of the right hand. the 
SustainPedal.X-offset is not working.

What's the right way to do so?

Thanks!

Robert