I was taking a hull of the whole button negative shape in many places,
rather than a hull of the sliced shape, which meant the amount of
decorative plate beyond the button holes varied depending on the exact
positioning of how it was sliced. this was brittle in general, but
more importantly made many plates too big when I cleaned up some code to
remove an override that I thought was irrelevant --- it was actually
affecting the overall geometry outside of the slice
Signed-off-by: Brian S. Stephan <bss@incorporeal.org>