@danmar123 As a user of a SP10 MkII seated upon a P'holz Plinth, along with a group of other users of the same TT and Plinth material, it is now mandatory to have a Phenolic Resin Densified Wood Board used a Sub-Plinth.
Panzerholz is the material generally used, but there are other options for this material from other Brands, Permali is also being used.
The material shown in the Link is available in the US, in many different colours, all info strongly suggests it is a ideal Resin Impregnated Densified Wood material, even though the weight can’t be identified as being approx’ 1400Kg/m3, or if it is a Delignified material. I would suggest to get to over a 1000Kg/m3 Delignification is occurring.
https://www.professionalplastics.com/professionalplastics/content/downloads/DymondwoodColorsSpecsFab.pdf