This work presents the experimental evaluation challenges of the modal effective Electro-Mechanical Coupling Coefficient (EMCC) of a hybrid sandwich plate, made of regular (hexagonal) Aluminium honeycomb core and woven glass fibre-reinforced polymer composite faces, on which is bonded a piezoelectric transverse response (d31) Macro-Fibre Composite (MFC) large patch. The testing challenges come from the very light weight of the hybrid sandwich panel and the resulting difficulties to consider, without damaging it, different mechanical boundary conditions (BCs) along its lateral edges. This experimental campaign, using an impedance analyser, complements an earlier one that used an LCR meter. The latter provided only the EMCC of the first three electromechanically coupled modes under free-free (F-F) BCs, while the former reached more accurately eight ones for F-F and clamped-free (cantilever) BCs. Beside graphical form, the obtained frequency and effective EMCC results are given in tabular form, so that they can be used as reference for validating/correlating future numerical models.