OK, i surrender, sorry.

But did you really like something like this:

F = #(let ((m (make-music 'ArticulationEvent
                          'articulation-type "flageolet")))
       (set! (ly:music-property m 'tweaks)
             (acons 'font-size -3
                    (ly:music-property m 'tweaks)))
       m)

\relative c'' {
  c4^\F c4_\F
}
[download]

Shit, looks like elisp ;-)

Update: BTW, Avid killed Sibelius.

My best regards, Karl