This letter proposes the experimental validation of an optimisation method for periodic metasurfaces. A previous study showed the design and simulation of a classical anomalous reflecting metasurface and enlightened the parasitic reflection induced by the translational invariances of the structure. The method applies to periodic structures, in the framework of the Floquet analysis. It consists of the exploitation of the Floquet type simulation outputs of a periodic element of the structure to predict the behaviour of the complete structure in terms of radar cross section (RCS). The proposed application focuses on the reduction of the RCS level of the structure in one particular Floquet direction. The fabricated metasurfaces and experimental setup are presented with the associated measurements. The well-agreeing simulation and experimental results validate the proposed optimization procedure.