Adjust decal falloff?

So I’ve noticed that there’s a falloff for the decal object that scales depending on the size of the decal box. For example, if the decal box is only barely clipping the ground, the falloff will make the decal somewhat transparent. But if the decal is centered on the ground it will show up just fine.

Does anyone know if there’s a way to adjust this falloff? Ideally I’d like it so the decal’s opacity is the same no matter how close to the edge or center of the decal box it is.