You can also compress the springs a bit using the threaded rod and plates, then tie some (strong) wire around the coils 2nd from the top to 2nd from the bottom in a couple of places. Then insert them in place, replace the balljoint and cut the wire. I've done it a lot and it works fine. The wire is removed from under the spring by prising the coil with a flat screwdriver and pulling the wire out. Piece of cake!

I'm running standard V8 WB RTS springs that I cut one and a half coils out of and it's low without being stupid-low (and still rides good too).

And as "thatotherguy" says, with super-low's you won't need to compress them much.