I've gone back and looked at numerous threads as well as all the info. on vender sites, and I am still puzzled. Are shims required with increased spring arc/lift, increased shackle length or both? My 4" Skyjacker lift was just delivered and I'm looking to order new stock or +3/4" length anti-inversion shackles as well. Will I need to shim the springs with this set up? Hate to ask all these questions, but you guys are a wealth of information and I would like to get the lift right the first time.