center figured bass vertically

[mari+lilypond]

Hi all,

if figured bass is drawn below a system it is automatically centered
vertically in one line. How can I achieve the same if figured bass is
above a system (see example below)?

If it can not be done automatically, how can I do it manually?

Any help is welcome
Markus


version "2.19.82"

cello = \relative c' {
  f2. f4
}

figuredBass = \figuremode {
  <3>4 <4>2 <3>4
}

\score {
  <<
    \new Staff = continuo
    {
      \clef bass \cello
    }
    \context Staff = continuo
    \figuredBass
  >>
}