Let me start buy saying I just did the rear end separation on my 1972 31' International.
What I noticed once I got it apart was that the frame had sagged away from the shell. Due to the extra weight of the rear bath and no frame reinforcement kit at the axle mounting area. (This also was fixed another story another time) What had happened was the frame at the bottom of the end shell had cracked at the same location it was bolted to the main frame rail.
So I had to splice in a new floor bow in. I did this by cutting a new one and then splicing this in to the old one. Then taking my rib coming down and also re-fastening it to the new floor bow. I also replaced some of the flooring that over 30 years had seen a bit of water
. Once I had all of this accomplished I then jacked the back end up level until I had a nice tight fit to the shell. Then proceeded in re-fastening this all down. using 3/8" bolts at frame rail.
I skipped the details on drilling out the rivets and then having to put in new olympics.
In this process I had learned that my frame rail was a little bent. This is something that I was unaware of at purchase. Not much had been discussed on this in this forum that I had seen or even had found prior to this at any other Airstream site. But it was installed after removing the axles and installing the reinforcement steel that Airstream does sell.
In this process I looked at the axles and they are sitting just at neutral to the slightly positive side under load(maybe 4 degrees). This means they are good. I have called the manufacture that said under load they can have up to 21 degrees (positive) and still be considered OK. But keep in mind this is the very high end of OK. Any more and there trash.
If you are not under load and are already at a positive angle it is time to replace these axles.
Keep in mind that if I was going to travel the country I would seriously consider changing these axles. Even though QDS told me that up to the negative angle of 21 degrees it is still OK. For my use which will be for only short trips. This is not at all something I would consider. I will be doing weekend trips to extended trips within 100 miles of my door.