alignment of text in TextSpanner

[libero . mureddu3]

Hi,
I'm modifying the "line-arrows.ly" example of the regression test in order
to create some indications in a cello piece. I've modified the edge-text
property in that way:

\relative c'' {
  \override TextSpanner #'edge-text = #'("s.p." . "ord.")
  \override TextSpanner #'bound-padding = #1.0
  \override TextSpanner #'dash-fraction = #'()
  \override TextSpanner #'arrow = ##t

  a8\startTextSpan gis8 a4 b4
  b,4 | g' c\stopTextSpan c
}


The problem is that the second word "ord." is aligned on the basis of the
letter "d", I suppose, and because of this is misaligned compared to the
arrow and the first word.
Any suggestion to have the same alignment? There is a property to change
in order to achieve this?

Regards,

Libero Mureddu

.