Not sure about the 4 in, but I installed the 2 in four years ago and the springs are just fine. The only thing I noted is that I used the HD springs and ended up with about 3.2 in lift...you might get more also. Check with Dave at Northridge for
good details, but I doubt the springs will sag, and in fact, this is the first I have heard of this...now RC, then yes.
08 JK 23S - Colorado Jeep Club No. 204
Too much to list - see my profile for details on build
16 JK Rubi with all the trimmings
NRA Life member
"It takes a special kind of stupid to believe criminals will follow gun laws."
I do not consider myself a smartass. I point out the obvious, search for the truth, and speak fluent sarcasm. I am, by experience, an accomplished curmudgeon.