It has a shelf, but not one that you could readily use for a single-emitter setup. The reflector area is more shallow than most C8’s. And the shelf has a hole in the center (meant for screwing the reflector+MCPCB assembly into place from below), so placing a single emitter on top of that would be a bit sub-optimal as far as heat transfer path is concerned. Also, the wire holes are in unique positions, so some additional modifications would need to be made there, as well. There’s some good info and pictures in this thread
