How can I change slur from above to below notes when switching staff in Lilypond?

Question

I have a music passage that crosses from the bottom staff to the top (in a Grand Staff) with a slur. But, I want the slur to go from above the notes on the bottom to underneath the note on the top staff. Is this possible in Lilypond (version 2.18.2)? How about 2.19.x?

In the below image, the top example is what I want, but the bottom example is what I get with Lilypond (typesetting code below the image).

\score
{
  \new GrandStaff
  {
    <<
      \new Staff="up"
      {
        \clef treble
        \time 3/4
        \relative c'
        {
          R1*3/4*2
          s1*3/4
        }
      }
      \new Staff="down"
      {
        \clef bass
        \time 3/4
        \relative c,
        {
          r4 c4^(^\pp g'
          c g' c
          <<
            { \voiceOne
              \change Staff="up" e4) b'4\rest b4\rest
            }
            \new Voice
            { \voiceTwo
              s4 d,,1*1/4\rest s4
            }
          >>
        }
      }
    >>
  }
}

Answer 1

Control points can be overridden. The pairs here are x,y coordinates:

      \version "2.19.80"
      % ...
      r4 
      \once\override Slur.extra-offset = #'(0 . 6)
      \once\override Slur.control-points =
      #'((1 . -6) (4 . 1) (13 . -6) (18.5 . 0.5))
      c4^(^\pp g'
      % etc

and give the image below which can obviously be improved with more work: