Daon,
I lost a friend in a car that came apart behind the front seats. He and his cousin both lost thier lives. This friend and his Dad ran a body shop. They found a really fast, powerful car but it had been wrecked. They took two cars and cut them in half and welded the good halves back together to make one. The unibody (no frame) car came apart at the joints where it was put together, while they were traveling at a high rate of speed.
I'm not familiar with the codes and regulations regarding this type of welding. Maybe someone will post something that will shed some light on the subject.
John Wright