Configuration doubleslur?

[Pieter Terpstra]

Dear people,
Don't know if it is possible but wonder if there is a way to get the topslur 
down to almost touch the noteheads?

Have this example for you:
\version "2.18.2"

\relative c' {
   \set doubleSlurs = ##t
  %\override Slur.positions = #'(1 . 1)
   \time 2/4 r8 <fis ais>[<d g>(<fis ais>)]
}

Thank you so much in advantage.

Peter