No worries that was my mistake. I set up my own decal material using the ‘Emissive’ Decal Blend Mode and was able to get the opacity mask through a Linear Interpolation. Use the images below as a reference on how to set up your own material.
Material Set Up
Material Applied as Deferred Decal
Hopefully this is the outcome you are looking for, but if you still need some assistance let me know.
Cheers,