Don't you mean mm instead of cm?
7mm is about 5/16 inch. 7cm is about 2-3/4 inches.
I have a hard time believing you cut almost 3 inches off a spring without major fitment issues.
That being said, I would like my car to be lower in the back so that the car sits almost level. I currently have DUB springs (Eibach Pro?). I was told that cutting the springs was a "bad idea (TM)".