"I'm back to wondering how water is getting into the interior. What am I misunderstanding?"
Bob,
If you look at the drawing carefully, you will see that the pin assembly goes into the bottom frame, the water was going around the pin into the frame, following the frame to the inside corner and running/dripping onto the floor.
Sealing the pin stopped the water intrusion and thus stopped the leak.
I don't know where the "drip pan" is located since one cannot see inside the the bottom after the slide is complete.
It is an assembly that Gulf Stream purchases and builds the slide into it.
It does work quite well and seals tight. No water problems since I had the dealer seal around the pin and that is what counts. Maybe the pan was sealed by a mistake by GS during assembly of the slide and that is what caused the leak, in other words maybe the pan was supposed to drip to the outside bottom but couldn't and that is why the leak accured, no way to tell. So the only option is to make sure no water flows past the pin which seems to be the best solution.
Anyway, it worked and I am a happy camper..
Ron