How to remove gap in UpPrall spanner?

[Javier Ruiz-Alma]

Is it possible to have the spanner join the upprall glyph in a trillspanner?

Looking to avoid the gap between the glyph and the spanner:

 

\version “2.18.2”

\relative c'' {

  \override TrillSpanner.bound-details.left.text = \markup{ \raise #1.0 \halign #-1.1 \smaller \musicglyph #"scripts.upprall" }

  \override TrillSpanner.bound-details.left.padding = #'0

  \override TrillSpanner.to-barline = ##t

  a4\startTrillSpan a a a

  a\stopTrillSpan

}

UpPrallSpanner.PNG
Description: PNG image