Layering high viscoelasticity ratio polymers into multilayered structure confronts several processing instabilities: viscous encapsulation, interfacial instabilities, elastic instabilities in the melts and elastic recoil of the extrudates. In order to conquer these difficulties, a novel slit multiplier die design, recently developed by our group, provides for lower pressure drops and much higher layer homogeneity. When coupled with an appropriate amount of external lubricants, necessary to provide the system with maximum wall-slip effect, thereby reducing the second normal-stress difference, polymer melts with viscosity and elasticity ratios as high as 10 can be multi-layered by the hundreds. The barrier and mechanical properties of the multilayer films of such highly rheologically mismatched materials are characterized, showing a much better improvement than single or bilayer films.