Baloney. The main lesson is that a well-known rear end place with a good reputation, and that I paid a significant amount of money to do it right, screwed up!
This is a routine job for them and I should not have to follow along second-guessing the professionals.
Weld the perches, weld the back brace, then put the housing ends on, and everything lines up.
But thanks for the victim-blaming.