RE1345 ZJ spring question

I ordered RE 4.5 ZJ coils for my son's XJ for XJmas. He has a heavy custom front bumper (95lbs) and he would like to stay around 4.5" of lift. Will these coils settle out to around 4.5 with the bumper or should I have ordered XJ coils RE1310? Over the long haul will these RE1345s work better?
Bumper pics; http://community.webshots.com/user/fallout96[/URL

Even with the heavy bumper those will net you around 5.5". What's he running in the rear? Maybe he could do something back there to level it out.