I think we did it!!!!   
Finally I think we have beaten the leaks!
Here's what I posted to a fellow sufferer who posted a plea for help on the Aliner owners Blog:

We have a 2008 expedition and have had constant problems with leaks. First in the left rear corner, then the front right and next the front left. We tried every way for Sunday to find the source but simply could not. In desperation we bought a couple of rolls of Eternabond tape and taped every possible seam in the dome windows, the vents and the perimeter of the roof sections. Still leaked!!!!!   #@$^%&*E$%@!#$#%%^Y  !!!

Then took off the dome window surrounds front and rear and took a good look at the windows from the inside. There were minute cracks (stress fractures?) in the corners of each of the windows right where the leaks were. We did some research and came across a product called .....wait for this....its worth it...... you won't believe it.....Captain Tully's Creeping Crack Cure. Available from a company called Vintage Trailer Supply at about $10 + S&H for enough to do several coats on each of the 4 upper dome window corners. You can also get it from West  Marine at twice as much.The stuff really works, but you have to be prepared to put on multiple coats, let it dry in between and then be disappointed by further leaks. However, the leaks will be smaller, so you put on another three coats, and eventually the leaks stop. If you are not so fussy about how the windows look from the outside then just get some clear silicone caulk and smear that around the upper corners of each of the dome windows. These seem to be the prime offenders for leaks.

FINALLY! we are leak free!

Fighting The Leaks! Still!
Yep we are still fighting leaks around the front dome window and around the roof vents. The right vent cover has given in to the sun and the hinges have fallen apart. Ordered a "Universal Replacement" from CYNDER.Com  but it is 14 1/2 x 14 1/2 " overall and what we need ins 13 1/4 square. Found that we could get the right one from Seven Os in Kirkville NY for just $15.
The Eternabond has not stopped the window leaks so we went to Captain Tyully's Creeping Crack Cure. Great stuff. We read about it on the Aliner Owners Club e-mails. It seems to have stopped the leaks from the hairline cracks in the dome windows, but the vents are still to be tested. A strange request for one who wants to go camping, but I would like to see some rain!

6/30/18       Getting the A-liner ready for the season. This may be the last summer that we use it before moving to NZ, or not, but we have some camping planned. First issue is to replace the front dome window casing as the old plastic one is broken and buckled, and just ugly. I bought some nice oak mullion that I joined to make a 2" x 1.5" angle stock from which to make the new frame. I'm mitering the corners and hope that I don't have to modify the opening too much ti get it to fit. Photos to be posted soon. The next order of business will be to apply Eternabond tape to all the external seams to try to stop the persistent leaks that seem to plague so many A'liners. More on that soon too.
7/1/18        The new window casing is made, now to sand, stain and install it. We put the first Eternabond stripping on the left side vent yesterday. It went on well, though is super sticky stuff to work with, not at all forgiving if you put it in the wrong spot!