Adjusting the upper tie of an octave

[Knute Snortum]

I am trying to typeset an e flat octave with a starting gracenote and held for two bars.  This much seems fairly straightforward: 

\relative c,, {
  \clef bass
  \acciaccatura { <ef ef' ~>8 } \tieDown <ef ef'>1 ~ | q1
}

The problem starts when I need to adjust the upper tie (because of other notes I've left out for clarity).  To get access to the upper tie I've tried this:

\version "2.18.2"
\language "english"

ignoreClash = \override NoteColumn.ignore-collision = ##t
adjustTie = \shape #'((0.0 . 0.0) (0.0 . 0.0) (0.0 . -0.5) (0.0 . -1.0)) Tie
stroke = \override Flag.stroke-style = #"grace"

\relative c,, {
  \clef bass
  <<
    {
      \ignoreClash 
      \tieDown
      \stroke \grace { ef8 ~ } ef1 ~ | ef1
    }
    { 
      \ignoreClash 
      \tieDown
      \stroke \grace { ef'8 ~ } \adjustTie ef1 ~ | ef1
    }
  >>
}

The problem is that the \adjustTie seems to be applied to the *lower* tie.  This may be part of the "voices get messed up with grace notes" problem that is a known issue.  My question is how can I do this?

Knute Snortum

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