Well, it's happened, a leak. Boo! Hiss! Boo! We have had a tremendous amount of rain, but a leak is a leak - must fix.
Fortunately, it's localized in the hatch, but the first time it leaked water found it's way into the cabin and soaked the mattress and popped up the tiles. Live and learn and patch and seal, repeat as necessary.
I bought a rubber garage seal and some 1/8" flat aluminum stock that I'll put over the hatch hinge, plus 1" of overhang on each side. Hoping this will work.