Tweaking Y-offset of an accent with a slur

[Knute Snortum]

I can tweak the Y-offset of an accent if there is no slur, but with a slur, Y-offset doesn't seem to "respond".  How can I tweak the Y-offset of an accent when the note is slurred?

\version "2.19.15"

\relative c''' {

  c4 ^\tweak Y-offset #6 -> ( a ) c -\tweak Y-offset #6 ->  a 

}

Knute Snortum

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