In order to reach the new 2020 CO2 emissions regulations, we have developed a wide range of lightweight noise treatment technologies going from pure absorbing to highly insulating ones, depending on the pass-through quality situation. This Generalized Light-Weight Concepts family was first optimized using the 2D Transfer Matrix Method (TMM) combined with quick SEA approaches. Taking into account thickness 3D maps with TMM is an efficient and quick intermediate “2,5D” optimization method, but it is not a real 3D approach.This work presents a new 3D optimization procedure based on poroelastic finite elements including intermediate cavities (like Instrument Panels) for designing these Generalized Light-Weight Concepts. A parallel reflection deals with products and processes in order to check the feasibility of the resulting 3D optimized insulator designs. Indeed, playing with multi-layer insulators (typically three to four layers) leads to some design difficulties for the low thicknesses, typically below 10 mm, especially for felt layers for which a maximum compression rate exists.This 3D optimization procedure takes into account the design freedom offered by each porous material technology, like foam or felt, but also plays judiciously with airflow resistances of porous layers or non-wovens, as well as compression rates of foiled backed light “fiber septums”, where bending stiffness allows switching from an absorbing behavior to an insulating one etc… This paper illustrates various applications of these Generalized Light-Weight Concepts with and without the influence of pass-throughs as well as intermediate cavities like Instrument Panels, modelized and optimized using 3D poroelastic finite elements and correlated with measurements in coupled reverberant rooms.