A little background on tunnel support in the various Pac-man roms. Pacman supports horizontal tunnels and Jr. Pacman supports vertical tunnels (you'll see that in the Teddy Bear maze). I did some digging around for the various Pacman variants that Bob released over the years following Pacman. Luckily they all have the same rom locations for mazes and graphics so they work in my editor!
While looking at Hangly Man's 2nd level I noticed something interesting...
Yes that's a vertical tunnel. Apparently the logic for vertical tunnels was included in this hack. There is also a level in Pac-man collection with a vertical tunnel so the code made it's way there as well. A word of caution, depending on the location of the tunnels it can have unpredictable results such as floating ghosts.
I tried this on a WIP hack of Caterpillar, which was an arcade hack of Pacman. I present Hangly Caterpillar