I have the OME hd lift springs in already. I just purchased the Rough Country 2" spacer lift kit. My question is how much forward movement will there be with the rear axle? I have read on a Grand Cherokee site that at 4" lift, the forward movement must be countered with longer rear control arms. If they must be replaced, do both the upper and lower need to be replaced with longer arms or would just the lowers be enough? Any opinions or first hand experience would be appreciated. Thanks guys.