\version "2.13.3"
\pointAndClickOff

smallFlageolet =
#(let ((m (make-music 'ArticulationEvent
                      'articulation-type "flageolet")))
   (ly:music-set-property! m 'tweaks
     (acons 'font-size -2
       (ly:music-property m 'tweaks)))
  m)

#(ly:set-option 'debug-skylines)

% \displayMusic 
\relative c'{
  % single flageolets work:
  <e d'>_\smallFlageolet
  <e d'>^\smallFlageolet
  % flageolet above and below does not work:
  <e d'>_\smallFlageolet^\smallFlageolet


  % If I move the flageolett away from the stem, how can i make it fall down towards the staff?
  \once\override Script #'toward-stem-shift = #-0.6
  <e d'>^\smallFlageolet
  \once\override Script #'toward-stem-shift = #-0.6
  <c g' g'>^\smallFlageolet
}