I'm building a stack stone wall about 2 feet high separating 2 levels of the lawn. There are lots of voids in the rocks at each layer and that's my question: It is smart to spread some crusher-run stone between the horizontal courses (back from the face so nothing shows) to fill in the voids at that level and below? ANd to get a better and smoother 'seat for the next course? Not ot have any thickness but just to 'level out' and fill the voids so the rock might have fewer wobbles? Any advice?