Modern Densified Woods by their very design are produced to be a material which is low in conductivity and selected for its properties where it is resilient to change when submerged in water, the Spec's show minimum uptake following 24 Hours Submergence.
Drawing on my whole experience of P'holz from the long-time owners, who steered myself toward the material, through to the most recent owners I am in contact with. Where across the Group, thicknesses up to 32mm are in use.
The purchase guidance given has been to buy Cross Grain Construction in B25 with a minimum thickness of 25mm.
There is absolutely nothing made known to me to over many years of knowing P'holz users to suggest a Cross Grain Lamination Structure in B25 of a minimum of 25mm Thickness is showing a tendency to warp.
I have my own supply of P'holz for nearly 18 months now.
A P'holz Plinth Produced, that is not in my possession at present, it is out on loan to an owner of the same model TT, the Plinth is produced for.
Additionally, I have a batch of boards that are cut to a dimension of 400mm x 500mm, I have just put a steel rule across these, and can report there is nothing seen to be considered as a concern.
I am even familiar with a Standard Type Head shell design made from Cross Grain B25 P'holz that is now about six months old. I was handling a couple of the produced Items from a batch only a few weeks past. The Material to receive the Cart' is approx' 4-5mm in thickness, there certainly has not been any obvious signs of showing a deformation.
I have no concerns for the above production specification for a P'holz material.
There is another specification for P'holz, where it can be obtained with a Longitudinal Grain Structure. A board of this at a particular thickness might have a tendency to warp, but I am not familiar with boards created using this Grain Orientation on P'holz.