I'm not sure that anyone reading it knows exactly what the situation is. It sounds like the inner and outer pipe are no longer connected, true?

I don't believe that most welding shops will have a spot welder that will work on material that thin or in a space that tight between the inner and outer pipe, but I could be wrong. I would definitely try and get it spot welded back in place. If you can't find someone local to do it, you might see if you could get Tam to do it.

I'm not sure if it would be possible to strap the outer pipe in place well enough to keep it from moving without crushing or denting it...

Bob