I am using the S10 rear leaf springs in the rear of my 86 4Runner, but am going to add another leaf to them to gain a little lift/stiffness for the saggy end syndrome. without loosing too much flex as they perfromed quite wellwith the the three leafs/load leaf removed. My questions is that the stock S10 springs have a small 0.12 inch thick rectangular plate between each of the three leafs. Any ideas what the plates are for? The only thing I can come up with is to make a softer ride for the road (more flexible that way). The reason I would like to know is when I add the extra leaf, should I introduce another shim 0.12 inch thick between the third leaf and the new one or just take out all the shims and make the leaf pack contact each other like the stock Toyota pack does it (worried it may make them too stiff)? Any help would be appreciated.