It would appear from what TimG has said above, that the bolt-in stiffening brace was not the solution to the cracking problem and Tim's chassis cracked 3000 miles after fitting the brace.
Tim, perhaps your chassis was starting to form cracks before the brace was fitted but at that time they were invisible to the naked eye under the paint.
Once again, another knee-jerk reaction from MMC that did not work.
