I have a setup I use in modo often where I have an item with a base material assignment, then that is instanced among various mesh groups. I use the same mesh with different graphics by creating a group in the groups panel and adding specific instances to the group. Then create a shader item mask for the each group and add any override materials to those groups. In this case I have a pressure gauge that is part of a regulator. The gauge is the same for inlet and outlet, except for the graphics on the face. The gauge is also used on 9 different SKUs. So normally I would have a shader item mask for the SKU, and in that an item mask for the face material, and in that one mask for inlet group and one for outlet group. I just place the relevant face graphics into each folder and works great. It seems though that Octane does not recognise the item mask on a group. Even if I drop them down into the base material they are ignored. The material is Modo, no Octane override.