Minecraft wiki entry for Mining, associated text: At the hub, mine down the same as if they were going to make a Central drop Shaft, but continue until they are on the same level as their next hub, depends on the size of their push, like a 8 push would be 8 blocks down. After they reach the bottom, make another hub in the same style as a Central Drop Shaft. This will require more ladders, so it's not a very good idea if players are short on log, but it allows a certain maze quality.