I had that same goop, and in the same location, on the '85 Westy when
I bought it.  It was extremely tenacious, almost like melted raw
rubber or something - I got most of it off but was never able to get
it all.  I kind of thought it might be old nail polish that had gotten
pliable and sticky.  I tried lots of different cleaning agents, even
tried unsuccessfully to scrape it off - it would stretch a little bit,
then snap back into place.  Weird.  Must've been part of the same
alien invasion Mr. Squirrel experienced.

Maggie