Figured bass extender line problem possible workaround

[liang seng]

Hi, I'm trying to find a workaround to the extender line problem in figured 
bass in Lilypond development series 2.7.2x. Here is the file:

\version "2.7.23"
\header {
}
<<
\relative { c c c c \break c c c c  }
\context FiguredBass \figuremode { \set useBassFigureExtenders = ##t \set 
figuredBassCenterContinuations = ##f
\set figuredBassAlterationDirection = #1 \set figuredBassPlusDirection = #1
<10 3>4. <10 3>8 <6+ 4>4. <6+ 4>8
<10 3++>4. <10 3++>8 <6+ 4->4.  <6+ 4->8 } >>

In the attached file figbass.pdf, the extender line problem is highlighted 
in the 1st bar. As you can see, the extender lines in the 1st bar are not 
horizontally aligned. This appears when there is 1. A double digit figure 
with a single digit figure and 2. A figure with a right sided accidental 
with a figure without accidentals.
In trying to find a workaround, I have tried to add right sided accidentals 
to the unaffected figures so that the right sided horizontal alignment of 
the figures as well as the resulting extender lines are more or less aligned 
properly (bar 2). However, the only problem here is how to make those extra 
accidentals (the double sharp in the first figure and the flat in the 
second) disappear. The problem with overriding the transparency of the 
figures is that the entire figure with the accidental will disappear instead 
of only the accidental. I also tried using the BassFigureContinuation object 
to move the individual extender line but I can't since it moved the entire 
double extender line. Any ideas on how to make the individual figure 
accidentals disappear without affecting the main figures?

figbass.pdf
Description: Adobe PDF document