depends how low you go! my unscientific method is to set it so the slack is just taken out of the spring, and so far ive not locked up the rears. the problem comes if you proper slam thge car, then there is no more adjustment left in the spring.
in this case I have someone stretch the spring, which involved putting it on a vw widowmaker jack and slowly unwinding it, inside a bin to prevent carnage should the spring ping off!
