The structures of wood, concrete, reinforced concrete, sandbags, sand, cinderblocks, natural stone, steel ( homogenous ), container are contradicting and not in the real proportion.
I heard the relation in comparison to armored vehicles is also off, but I have not tested or compared hardened armored plates with the rest.
As far as I understood, you can only change the individual resistance by editing the .p3d files, which is not allowed, as far as I know.

Since I dont think BI will invest that much time and effort to set correct values for each model, again, I suggest to give another opportunity to the community to find those values for ourselves, that can be by letting us edit the models or some way to use config entries to do that without editing the models.

I am interested in a workaround.