In figured bass, specially designed glyphs for 6\\,
7\\, and 9\\ are used by default. Similarly,
specially designed glyphs for symbols 2\+, 4\+, and
5\+ are used by default if plus signs appear after the number.
To change that, pass an alist to figuredBassPlusStrokedAlist and
set the glyph in question to #f (or omit it).