ANSYS Bilayered diaphragms .A parylene layer (viscoelastic material) to protect the diaphragm of a sensor

Dear Colleagues,
I am working in the design of one packaging for pressure sensor (piezoresistive), this packaging should be really cheap, I want to use a layer of parylene to cover the surface of the Silicon Pressure sensor, which include the diaphragm with the piezoresistive materials, I am using ANSYS to select the optimal thickness of the layer of parylene.

Currently I am using a simple linear and isotropic model, that is just a diaphragm of silicon of thickness 80 um and over the this diaphragm, a layer of 4um of Parylene, I am just interested in know the "cushioning effect" of my the extra PDMS layer over my sensor, that is, the loss of sensitivity. The data for the PDMS I am using is:
Young modulus 2.7 GPA
Poisson Ratio 0.4

Then I am applying the pressure to the model over the Parylene Area, and getting the displacement and stress in the area of the diaphragm of my pressure sensor, that is, just below of the parylene layer. Is this approach correct? I found some papers using an approach very similar to my idea, but I want to check with you guys. What I want to know is the effect of the Parylene layer on the performance of my sensor.

I hope you can help me.