TrillSpanner inside slur

[Toine Schreurs]

In the next example, the first two bars have trills outside the slur.
The \trill can be moved inside with \override Script..., shown in
bar three.
Is it possible to move the trillspanner also inside a slur?
I tried \override TrillSpanner... but without success.

\version "2.11.32"
\relative c'' {
  c4( d^\trill d^\trill e)
  c( d\startTrillSpan d\stopTrillSpan e)
  \override Script #'avoid-slur = #'inside
  \override TrillSpanner #'avoid-slur = #'inside
  c( d^\trill d^\trill e)
  c( d\startTrillSpan d\stopTrillSpan e)
}

Toine Schreurs