add_extension - remove_extension isn't adding all styles

In an effort to make a tabbed heading we modify the styles for different props by adding and removing extensions like so:

heading.style.add_extension(unselected_style)
heading.style.remove_extension(selected_style)

Unfortunately not all the styles change. The border does not get added to the new style, nor does the hover. The old hover does not disappear. The unselected and selected styles are below:

selected_toc_heading {
font_face "Arial Rounded MT Bold" background_color "#D8F0BB" }

unselected_toc_heading {
font_face "Arial Rounded MT" bottom_border_width 1 border_color "#AAA" background_color "#DDD" }

See the Erics for details.