Considering you're running the box set-up and not something really "off the wall", adjusting it to try and get rid of the chassis slap isn't normally done or really a good idea IMO. Trying to adjust for the chassis slap is going to hurt the rest of the set-up more than it's going to help with the slap, IMO. Making the b4.1 less aggressive isn't something I've wanted to do so I'll let others help you with that one, other than the obvious tire choice option...