FWIW - I installed the RE 4" std. about a month ago... Keep looking, I don't think it lives up to the hype. I ended up with 6" of lift and it's stiff as h3ll, and has minimal droop. BTW - I have checked my shackles and they are not too tight. Also I have put several hundred miles on it, it will flex, but, it does not live up to my expectations. Your results may vary... (I still need to get bigger tires - good thing I waited to see how much lift I got out of it!)
On the good side - I don't think my gas tank skid is gonna take a beating anymore. It does ride better on the road, just a little bit more squirrly due to higher CG.
Just my $.02