We have created a preliminary version of the Octane materials. Please, do this:
1) Download GravelOctane.zip
2) Unzip the file in C:\Program Files (x86)\Itoo Software\Forest Pack Pro
, replacing the existing files.
Because the Octane bug that ignores Geometry->Material, each time you load a preset it's necessary to assign the material to the Custom Object, as described in my previous post.
In next updates, we'll try to implement a workaround for that (probably assigning the material to the object automatically).
If you find some problem with the library, please let me know.