The first applications of plastic panels in the underbody targeted weight savings (elimination of the PVC coating) and aerodynamic drag reduction.The potential for the integration of acoustic functions in such new elements, addressing both interior and exterior noise, was readily recognized and demonstrated in several studies. These also pointed out the synergic interaction of the new elements with common systems and components of the sound package.While it was rather straightforward to define an acoustic design and optimization process, based on material modeling combined with component, system and vehicle SEA and FEM simulation, it also became clear that the integration of acoustic functions involved many problems that needed to be addressed in a multidisciplinary approach. This must consider the underbody elements as a part of a system having to fulfill functional requirements related to exterior and interior noise, aero-acoustics, aerodynamics for drag reduction and driving stability, thermal protection, thermal management in the engine compartment and in the tunnel area, protection of the body, assembly and durability. The harsh environment involves development of materials able to stand all the related OEM specifications, particularly demanding when the elements are designed to provide absorption in the cavity beneath the vehicle.After a brief historic evolution and the state-of-art in underbody systems, the paper describes the various vehicle performance tuning options, including acoustic function integration. Several measurement campaigns demonstrate these important contributions.Aerodynamic improvement up to 10% drag coefficient reduction, lift force reduction and noise reduction potentials up to 3 dB are shown. Since the management of thermal reliability and feasibility is elemental in those applications, this paper also describes thermal implications and solving strategies for an optimum and reliable solution.Finally, concepts for cost minimization need to find place in such an analysis, in order to demonstrate successful routes for new applications.