I...I was doing GREAT on my new embark, tetrahedrite, 150 FPS ON MY TERRIBLE COMP!
Do a 2x2, change cavern layers to 2 with magma layer on. You should get an average of 30z levels.. I think you'll be ok.
What exactly do you have to tweak to get an average of 30z levels? Isit in the world gen parameter files?
Yes, generate world with advanced parameters on the main menu screen.
There's a few options in the world gen parameters pertaining to cavern layers and Z levels between them. Select your world size and hit e, it'll be a few pages down.
I suggest making it around 5-10 z levels above ground, 8 z levels before first cavern layer and changing cavern layers to 2. There's another setting like Bottom Layer (forces magma). Make sure that's on if you want adamantine and HFS.
This way you'll get all the features of the game as far as digging deeply goes, including one cavern layer thats very easy to dig to, (8 z levels below ground, but if you embark on a mountain you'll get more z levels going upward), as well as the magma sea and the circus.
I also recommend building your fortress vertically for maximum efficiency and least pathfinding, deleting clothing from the raw files and shutting off weather and possibly temperature. Temperature is Fun though, but I find weather adds little to the game for dropping off so much FPS.
You will maintain very high FPS even with many, many dwarves this way. By the time the game gets dry for you with these settings, you'll have figured out what you want to tweak to keep high FPS.