We're in the process of restoring our 1969 Avion which is very similar to an airstream. I think airstream may have even made Avion at one time...anyway, we're having trouble with leaks. We have sealed by caulking and some type of spray tar every nook and crevasse we could find but during heaving rains we're still getting water intrusion. We're at a stopping point with the restoration because we're not sure how to proceed. Any advice?? Any sealant that works better than others? How do you find where the leak is coming from? Thanks!