@tomic601 The individual that I refer to as the Godfather of using P'holz for Audio use, has supplied information on their Qualia Labs Website about many materials measured damping/dissipation.
Their follow up exchanges that can be found on various forums, strongly siggests that when it comes to Board Thickness, a 10mm Board Thickness, is all that is required for a Phenolic Resin Impregnated Densified Wood (PRIDW) to attain the most desirable measurements for Audio Purposes.
I have been demo'd plinths made from Laminations creating a 35mm Board Thickness and from a typical production Board Thickness in both 25mm and 32mm. The detected differences on a Sonic in these thicknesses, are not as immediately discernable as when a PRIDW Plinth is compared to a standard Birch Marine Plywood, or a non-resin impregnated increased in compression Plywood.
I have a PRIDW Board of a 75mm Thickness, this is selected to embed my TT's Motor Unit into when I put together my own SP10 MkII Kaneta Design.