Vertical alignment of Figured Bass?

[Rutger Hofman]

Hi list,

how can I achieve better vertical alignment of figured
bass figures? See example.
My preference is between:

a) the top of the stack of figures is at some fixed distance
  below the lowest note in this *bar*
or
b) the top of the stack of figures is at some fixed distance
  below the lowest note in this *staff*.

In all cases, I would prefer the alignment to be "top" i.s.o.
"bottom".

Any tips? I tried:

\property FiguredBass . TextScript \override #'self-alignment-Y = #'-1

but to no avail.

Thanks,

Rutger