you generally need to change to short strokes at lower than a 50mm drop
if you were going to short-stroke a ke30, you'd change to corona coilovers on ae86 power steer arms and get some decent brakes while you were at it. little corolla struts and brakes aren't worth the cash. i think anyway. pajero master cylinder and 14" wheels required
i don't know why you'd want to lower a 30 more than 2 inches anyway, i think they look silly scraping the ground, and the usefulness of the car becomes an issue, driveways and speedbumps and such. i enjoy being able to drive over gutters like i just don't care
but yeah, like the others said, stock spring diameter is huge, so you'd open up next-to-no negative camber with adjustable tops. this is why i suggested changing to ke70 struts, smaller diameter spring rocks