Not sure what I need for my rear end after looking at the Carli site. Would the 5 leaf add pack be sufficient for better rear end ride or should I go with the full progressive leaf pack? BIG price difference, but I assume the 5 leaf will get rid of the that 2x4 ride I have in the rear? Already have the coil springs, just want to balance the ride out so the rear isn't bouncing me all around. Any other rear upgrade suggestions? thx