Probably not what you are looking for but just food for thought, there is a guy in Germany that made
a column support/brace/girdle a long while back that when added is supposed to give the bf20 much better stiffness.
They used to sell kits but seems to be down now but there are plenty of pics to see how it was built.
This is the google translated page.
Go to engineering projects page 2, girdles for the bf20.