That argument could only go so far. Mathmatically, the town would end up eating itself out of reality.

Let us say that there are 100 people in the town. Let's say that there are exactly 50 men and 50 women. To sustain taht many people, you are looking at two pounds of food per person, per day. That is a total of two people a day being eaten on the first day of this study (400 pounds, but about half of that is bone - so two hundred pounds of actual flesh).

Granted, the numbers would adjust themselves as there are less mouths to feed. They would also be adjusted as children are born. Remember, though, it takes 9 1/2 months to have a child. Also, that hild would not feed more than two people for one day.

Without pulling out the calculator adn doing all of the math, my estimate would be that the town would devour itself in roughly 45 days (give or take a few).

Now, there are ancient civilizations that fed themselves mostly of human flesh. This flesh came from outside, though. Usually travelers, enemies, and slaves.

Well considering there are other answers here already, I'm going to make a few assumptions. You say they augment their diet with fruit/vegetables - I'll add some grains and breads which is reasonable I think - so that makes them a vegetarian community, when they aren't eating each other.

Let's also say that they consume meat once a week, and again that's not too unreasonable if you look back on primitive tribal societies. So each week they have a huge feast of long pig and this is shared out between everyone.

Let's say that an average sized sacrifice would be about 50kg and most of this is consumed. A feast night for one person would involve eating about a 1.5kgs of meat, to be generous. That means the average sacrifice can feed about 33 people or up to about 50 people if they each each 1 kg, which is still heaps!

Now I'm hoping for a MATH GENIUS to come along and help me work out a sustainable population given that 50% of the population is female ( a good figure to use I think )

Some females will be infertile.
Some females may actually acquire mates from neighboring villages, increasing the base population.
Each fertile female can produce a new child every 18 months, giving them time to recuperate slightly each time :(
Each female has about 30 years to bear children

The community wouldn't eat the females very often, only the infertile and the sick ( I guess )

so...how do I finish this?? What sized population would survive ? if they could ? would it work if they only had a feast every month ?

argh!

This is but a short and quick answer to the question of surviving as a cannibal. A society of cannibals would adjust to the environment around them. First and foremost they would not be inclined to reduce their numbers through self cannibalism, simply because the human mechanism for survival would not allow them to. The defense of their village would be foremost in their minds, and fewer people would mean fewer members of the society to defend their community against enemies. Before consuming members of their own tribe they would attack neighboring villages and even use insects or fish as a way of supplying protein to their diet. Normally cannibalism is used as a means of honoring the dead, consuming the spirits of the enemy ,or, as a last resort to satisfy hunger and survive. For those reasons it would only make sense that a tribe of cannibals will easily survive.

Yes it is certainly possible if they were technologically advanced and if their law permits cloning. I am sure they could industriously set up mechanisms to clone as many humans needed to meet the demands for consumption.
http://stuff4restaurants.com/blog2/wp-content/uploads/2008/08/cannibal-restaurant.jpg

If they could augment their diets with fruits and vegetables and assuming they need some compound only available in human meat to sustain, they could possibly find an extract which incorporates it and make pills out of it and take it as supplements. Because I am not too keen on eating my own kind. It would mess up your morale if you are going to be eyeing everyone you have relationship with as a potential prey, let alone people with whom you don't have a relationship with.

If technology is not allowed, then it is going to be difficult to control people who would be trying to kill one another to either fill their stomach or to keep others from filling their stomach with yours.