There are several idea to setup the layout of the acrylic layer,compliant layer and the diffuse layer.
e.g. (from top to bottom)

diffuse layer
---------
should there be an air gap?how to make it small?
---------
compliant layer
acrylic layer

between the diffuse layer and compliant layer, there should be an air gap, otherwise the system
will trigger FTIR constantly, but how to make a small air gap between the diffuse layer (e.g. rosco
grey) and compliant layer? it seems so hard, since the rosco layer is so soft to support its weight
in the center of the layer .The diffuse layer and compliant layer can easily be attached together.