Stripper rear - height difference?

[matt|H]

Last time I took the rear of my car out it looked stupid as it was high in the first place... Does anyone know roughly (or exactly! lol) how much of a difference it makes to the height?

Reason being I'm looking to get slightly shorter springs in the back and stripping it again so it looks "normal", until I can get coilies.

Guessing 30mm would be ideal...