ballooning a note including its attributes

[Jean-Charles Malahieude]

Hi all,

I need, for an examination paper, to add a ballooning over two 
consecutive notes. So far, so good I can play with the slopes, but how 
can I adapt the engraver to include the accidental (in other words 
emphasize the C-sharp, not just the C) and add some padding between the 
object and the boxing.

\new Staff \with { \consists "Balloon_engraver" } {
  \relative c'' {
    d8
    d8 <d-\balloonText #'(1 . 4.1) \markup { " A" }>
    <cis-\balloonText #'(-0.9 . 4) \markup { "" }>4
  }
}

TIA,
Jean-Charles