I'm wondering if this is what your actually refering to. Here is a photo of some rain / stone shields from an alloy decklid that is supposedly off a Factory ST , as you can see they do not attach there (of course someone could obviously bolt some thing similar using that spot for a fastener) :
PS - I have photos of similiar underside views of ducktails from a couple RSR's with rain shields.......they are not fastened on those tabs either , but just next to them as on the alloy ST lid posted above.
Plus , none of the Ducktails i've viewed with the holes in the two outside bottom tabs have any holes in the tail that would correspond to where someone would need to fasten the other ends of this type of shields. So unless it is a completely differant type of carb shield (like one piece for both cyl. bank inlets with a length spanning tab to tab , sideways, & not attached on the opposite side of grill opening)......I don't think so