I just removed the Steeda Ultra Light springs yesterday from the rear of my mustang and so far I am much more comfortable being able to get a finger between the rear tire and fender well. I still have the Steeda's in the front and actually like the way it is. I can't imagine any issues using 2 different springs in front / rear but I am a newbie. So my rates are now 200/740. Anyone running setups like this, is it too little rate in the rear end?