Simply put - You can install the piezo on the metal plate attached to your bridge plate, but we're not sure about the impact this will have on the tone of the amplified signal. Our piezos are designed to bond to the bridge plate wood so that energy transfer is maximized and the natural tone of the guitar goes directly to the ceramic elements. If you have a metal plate installed on the underside of the bridge plate, this will impact the the transfer of energy - but we're unsure as to what degree because there are different materials, shapes, and thicknesses in the market regarding these metal plates.