Originally Posted by Sh0velMan

^^ Your cautionary comments are valid and true, for the most part.

That said, for our cars, if you're lowered significantly, there isn't really any pre-load on the springs, so it's perfectly safe to adjust them.

This is for sure true in the front, and depending on setup, in the rear as well. Ever notice that if you loosen the shock nuts in the front, the nuts don't come up off of the tower? That's because the weight of the spindle/arms/brake/everything else assembly is pulling down on them because there's no assembly pre-load.

So for coilovers where you're adjusting a ride height adjustment that's independent of spring pre-load, you're just fine doing it on the car, as long as you can confirm there's no pressure on the assembly. (Which again you can confirm by loosening the top nuts and seeing if they stand up from the metal or if the shock just sinks down, keeping the nuts flush with the surface)