Set the world to stop at year 50 to keep kobolds. Anything higher is pushing it, since kobolds tend to get eaten by megabeasts fairly quickly, as far as I can see.
Eh? I'm guessing because their thiefyness conflicts with the megabeast raids? In the older versions, increasing cave number/size seemed to give them a foothold, but in the latest edition, kobolds don't seem to be able to claim caves as easily/at all.
Stopping worldgen at year 50 is just... no. Not an option for me. 1000 is my minimum, and I've had the 'bolds survive to that year, but not in a world with a single half-way decent (embarkable) site. I crank down the civ number, I don't see the 'bolds and the cave-animal-people show up at all; I crank up the number, and the humans/elves/gobs devour every single piece of real estate worth yawning at and do unspeakable things to my CPU while calculating the journey of Mook con Whatever, in which he killed/tamed/got eaten by wolves.
You may also want to tone down the number of sites (new worldgen setting) - this limits the "sprawl" that goes on during history.
Sites? As in civ number, or number of mountain/non-mountain caves? If it's just a parameter I've missed here, it would be awesome to feel dumb about that.
I've been trying to get some more evil too for additional Fun (TM) (R) (C) but I apparently don't know how to properly tweak the Evil/Good square counts.
My last try genning a world, I got a normal evil area (harpies/ogres/werewolves) instead of an undead evil area (no plants, and zombie groundhogs... oh the horror!) So it's not impossible to get Fun Evil areas in .14.... just, you know, kind of a pain in the arse if you also want stuff like sedimentary layers or sand or flux or plant life or less than four layers of aquifer.
(Still waiting for a combo evil area, personally... Zombie ogres. Herds of skeletal werewolves.)