counter top

Hi All, This is a system I came up with for securing small machines, tools etc. to a workbench top. Basically, it's a machine tool "slot & tee nut" arrangement, made out of common strut channel. It was a result of my commitment issues, except in this case instead of women, it was tool placement...

Does anyone know how flat the typical granite counter top is and its suitability for use as a surface plate? We will have a few cutouts from a kitchen remodel job and I'm looking for uses for them.