Curl,
I've never had the chance to find out as you really need to remove the extractor/ejectors to find out.
Dovetail lumps as you know are easy to see when looking at the barrel flats but it is a very different story with the shoe lump setup.
The shoe has such a large contact area that I doubt a dovetail would be needed.
Maybe someone here who owns a shoelump gun can have a look and let us know.