Here are some images. The first shows the range for door activation. Notice that the distances are not symmetrical around the center. (They are symmetrical around the NW corner of the center block, which is math-correct but visual-wrong.) This affects node design because most design have more than 16 distance between villager pen and opposite side doors. Leading to the center shift behavior. # This second image shows golem spawning area. Notice that it follows the same pattern with one extra block in the negative X/Z direction. Also note that the yellow line is out of range, but it must be open for golems to spawn next to it. This is because a golem spawns checks that there is open space to the north and east west. (edit:corrected direction) # To keep nodes from being ugly, most people even out the sides. I've added gray concrete to show the added non-spawnable area. I also added doors on the sides to show where the walls would go. Villagers are usually just outside the doors.
Here is my node design. First in the style above for comparison: Then in real form: Key ideas: There is only one villager location, which maximizes efficiency and drop rates. All doors are activated from that one location, so no shifting of node centers. To fit more nodes, I need the greatest distance between doors and next-center. By pulling the doors into the center of the node I gain 8 blocks in both directions! This is enough space to employ sphere stacking techniques to fit additional nodes.
