Here's my map so far.
http://mkv25.net/dfma/map-5559-boltedgirderI got somewhat different soil layers than most others. No flux, but sand usefully placed. Orcs and upgraded gobbos. Popcap was set to 18.
I decided to build a green glass cylindrical fortress inside the bottomless pit. Only about 8 levels done so far, but a lot of time was lost to tree cutting and hauling for the power plant. 272 water wheels. Disengaged from the pump stacks, they require 3380 power just to be idle. When fully powered, it should produce approximately 21,000 surplus power beyond the needs of the water and magma pump ladders. Anyone have any ideas what to do with the excess?
I dug out the river to bring water to the fortress and some surface area to flood for tower caps. I decided to expand it a bit more, branching off to the east and connecting it to the chasm and opening up a bit more tower cap space. At the chasm I hope to be able to catch purring maggots as well. Two GCS have been captured and set up in two silk farms above the entrance.
Once completed, I'll pump out the magma pipe and excavate 3-5 tiles around the fortress to the bottom and extend the moat to expand the magma pipe. I'm preparing for tunneling strategies for future versions. My idea for an entrance will be a green glass snake extending down from the easternmost edge of the pipe through the magma pipe and to somewhere 6-10 levels down where the new trade depot will be. Caravans will enter the mouth of the snake and descend through the magma. Below it will be a suspended glass mini fortress which will house the bedrooms.
Much to do yet. Oh, I have but one soldier. She's standing proudly in the center of the fort on the entrance level. 532 kills to her name, she masterfully lures orc sieges and massacres them in the depot space with her artifact iron crossbow.