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Any lower than that and it will look retarded. It sits perfect as is.heres a picture of how low it is now
Not if done correctly. But then again, after so many k's and time, springs sag anyway.
There is no such thing as properly, there is only one way to do it, they get heated up, spring compressor are attached and they are cooled down, thats the only way, it compromised the strength of the steel quite a bit. It saying that, I have not heard of someone breaking one yet.
Also I think it looks good how you have it now. If you always have loads in the back, it practical and it will sag quicker.