I am looking at using the Benissimo Granite Tile for kitchen top. They recommend 5/8" plywood with 1/4" cement board as base. Their bullnose pieces will cover this but nothing any thicker.

I have one top area with about 10" overhang so want to strengthen the underlay but would prefer to not go thicker. Was thinking of routing channels in plywood and embedding some sort of (like rebar) support rod into the underside of the plywood.

Comments, suggestions, etc???