Use Krazy Glue (or similar) between the piezo and wood, let dry, then apply a generous bead of silicone around the perimeter and edge of the piezo, and a good blob of silicone on the piezo wiring to help keep them from vibrating loose. Use Gaff Tape to secure the wiring that runs from the piezo to the jack to prevent them from vibrating.
Cheers
-A
Cheers
-A