Ottava bracket offset

[Andrew Bernard]

How can the ottava bracket in this snippet be moved downwards? I have been able to get it under the beam, but now the stems seem to be in the way. Using extra-offset and Y-offset appears to have no effect on the position. The result we are seeking is to have the ottawa bracket under the tall beam but much closed to the noteheads.

Andrew

\version "2.19.20"

treble = \relative c'' {

  \clef treble

  \time 4/4

  \override Beam.damping = #+inf.0

  \override Beam.positions = #'(6 . 6)

  \override Beam.outside-staff-priority = #1000

  \override OttavaBracket.extra-offset = #'(0 . -2)

  \stemUp

  \ottava #1

  c8 d e f

}

\score {

  \new Staff { \treble }

  \layout { }

}