Scaling Factor
This is an important step!
Not all avatars are scaled the same. This shader is sensitive to that scale.
To make sure that all the features work correctly, you'll have to let the material know about the scale factor of the mesh that the material will be applied to.
Automatic
Method A
You can right-click on your avatar in the Hierarchy view and navigate to ValueFactory/Fast Voxel Shader/Calculate Scaling Factors. This requires the voxel shader materials to be on your avatar.
This will not take into account VRCFury material swaps, animation clip material swaps or any other materials that are not effectively on the material.
Method B
You can select all voxel materials and then drag your avatar object from the scene into the Get Scaling field on all selected materials and click Calculate.
Manual
You can find the scale manually for your avatar by looking at the original scale of the Armature object of your avatar/asset/prefab.