When suspended in this harness (hula mic), we got the best results from a small styrofoam bowl, styrofoam dessert plate, and styrofoam clamshell, with or without food compartments. On a shape like the bowl or compartmental-clamshell, the piezo placement has an enormous impact on low end: if you have the option of partially extending the piezo off the back of the resonator, into space, it can add dramatically to the low end and increase the naturalness of the sound. Leaving it dead center gives the narrowest response, and the best “old time broadcast” sound.