I was first to find that tunnel I do believe, but my version didn't work after they removed the screen bounce back thing, well Im sure it could of, but cbf'ed trying to get it to.
Works on the offline mg of course, perfectly. If anyone wants the original just ask.
Note that as first player in a multiplayer game, the screen should not be moved on this hole to adjust to the screen position in the offline game (so far my own experience has shown). Shoot just how it shows in the "g" in Strength. Furthermore, most 1st shots on holes 16 and 18, but not all, should not be adjusted for shots crossing over between the offline and online multiplayer minigolf, though it seems you should. I hear that some find it difficult to eagle Hole 18 as second player in multi. Just simply bring it back to the original starting screen position Player 1 shot in and count your pixels. Do not bring it to the screen position the offline version starts in or you will miss everytime.