NOW you tell me
During a dry (Well, NOT raining) spell while in Portland, I grabbed a ladder and discovered the leak happening from my roof vent mounting. It was a couple screws with NO butyl tap under the outside lip!
I took the butyl tape and foil tape kindly given to me for just this purpose by one of our party goers in P Land and stuffed the leaky holes, remounted the rusted screws, covered the entire lip with butyl tape and covered THAT with foil tape.. 100% of the perimiter. No leak there anymore, it will get me home.
I did the same treatment around the front and rear windows
on the inside, and just the foil tape outside.
My trailer looks like the Beverly Hillbillies wagon, but I am dry inside!
When I get home, I am going to check into your duck seal and keep that in the trailer. Sure wish I had it on the way up!