I read plenty of post on the shocks just a quick question. I recently replaced all four shocks on my 2003 Yukon. Upon doing so I realized I have RPO codes ZW7 and G65. Meaning I have Nivomat shocks in the rear. They were clunking and bouncing as if they were blown. So I replaced them with some standard ones, later realizing I need to change the springs. Long winded post but my question is how long can I run the softer springs?