Iray decal on/over geo shell?

lemips

Is there any way to project an Iray decal onto a geometry shell, or force it to show up over the shell? I have tried attaching the decal to a blank shell with a higher displacement than the one to be covered, but I have learned the decal seems to go straight to the base figure geometry. 

I am trying this because decals are easily animated, while shells follow posing and morphs. Both properties are needed in the scene.