Adjustable Shackles?

Whats everyones opinion on adjustable shackles? I out new spring sin my car but I want the rear about 1 - 2" higher. Not a lot jsut alittle stance for it. I've had people telling m e to add a spring which I dont wanna do or get airshocks. But the shackles look cheap and easy enough. Any downside for a street car?