Putnam asked me to upload my 400-dwarf fortress so that he could take a look at it. I'll upload my three >400 dwarf fortresses which all exist in the same world. I am using the vanilla version of Dwarf Fortress without mods.

The first fortress is called Dyerose and was my first large fortress. It is VERY poorly laid out and I allowed the animals to reproduce in an uncontrolled fashion. There are over 400 dwarves and hundreds of animals, as well as some number of hidden enemies in the first cavern layer. The fortress typically runs at around 3-5 FPS. I don't consider this fortress to be salvageable but it might be interesting to take a look at in terms of the effects of a large number of dwarves and creatures on framerate.