I'm glad you've enjoyed solving this level. It seems you have found a shortcut, as I did design the level so that all tunnels in the first bit be covered before you leave that area. I wonder if I change the tunnel at F9 to #0 and the tunnel at F4 to #4, will your solution still work? I'm not necessarily going to do that, though, if it makes the level less interesting to solve. By the way, Donald helped me with the end bit and another shortcut the level had before, so thanks to both of you!
Regards, Gerry