Instead of subjecting the peizo to soldering iron, I used the sticky copper tapes instead. The peizo is cut with Stanley file. Make sure you choose a good triangular one, as it can be critical. Also make sure the force is moderate such that you don't cut the copper inadvertently, which is undesirable since any deformation of the copper plate would absorb peizo movement. I glued a copper part to the peizo base as the probe holder with epoxy adhesives 353ND 1LB, which has expired but that is what's readily available to me. Choose a softwire, i.e. thin wire for the connection as too stiff of a wire could damage the delicate peizo during later manipulations of the apparatus.