What is the smallest iron golem spawner?

I'm trying to create an iron golem trap, and while I can create huge ones (see screen shot below) I'm interested in making smaller ones. I have tried several different variations, including this one, and they don't seem to ever spawn a golem. There are tons of examples of farms on youtube, but from what I can tell they're all 1.2.2, granted farming in 1.2.5 is pretty inefficient, but I'm still interested in doing it. What am I doing wrong?

Solution 1:

12 doors on a side with 4 villagers per side. The vilage 'center' is the middle point between the the 'doors' that are considered to be part of the village. The golems will spawn in the middle and fall thru. DocM has a nice tutorial on youtube describing the mechanics in detail. 20x20x8 footprint for the main cells.

It could be that your layouts dont lend themselves to having a natural 'middle' Even the 2nd picture with the doors all clustered together in the middle, there might not be room for the golem to spawn because the doors are there.

Solution 2:

A village has to have over 26 people for an iron golem to spawn. I think it might only spawn when there is a risk to the town or the villagers are free to wander around the village.