I am very interested in what you come up with according to Steve's Key.
So please keep us posted on your findings :-)
My next step (unless someone else dives in first) is to go to the British
Library's 1931 photographic copy of the VMS (as I don't have anything like
a full copy here) early next week, and carefully work my way through every
image. That should let me determine the locations (and a fuller taxonomy)
of all the "long gallows" instances: as well as a table with the characters
immediately following them.
Once I've done that, I'll post all the results here: and we can try out
Steve's folding key theory on some real data, which is (fingers crossed)
where it starts to get really interesting...