I have had good results using different types of isolation materials in combination. In my system, I use various combinations of maple, carbon fiber, sand, and viscoelastic materials, sometimes combining as many as three different materials under the same component. I have found that combining materials offers a significant improvement over each material used individually. I have not, however, experimented with granite, so I cannot comment on the likely results of combining it with maple. But I think your experiment is worthwhile. Good luck.
