Is the frame supported and level?
When you look down the side of your Airstream from front to back, does the wall look like it's bulging out at the rear where the floor replacement is happening? If your floor was tight before you removed it, and you copied it exactly, you should end up with it tight again. If not, the shell has changed shape, and needs to be checked out as throughly as possible for sags and bulges. I was as careful as I could be and still have some places where the subfloor is about 1/2" away from the wall skin, but It's straight and has no bulges.
Best to you,
Rich the Viking