On my Duster project the original chassis shop screwed up the job. The boxes were built out of tin foil and the holes were drilled crooked. I had to take the car to a different shop where they used heavy duty steel boxes and they put the holes in the correct place. They had to cut the old boxes out of the car and grind everything flat and start over. That was a dirty nasty job. Good thing I didn't have to do that work! In the end it came out okay but it will never look pretty since the rework job left some scars.