I also used the Unimates. I do mix-and-match locomotives, but with DC, it has to be done by hand anyway, so dummy couplers aren't a problem. As long as both ends of the consist have working couplers, the ones in the middle are going to stay together, one way or another! Since I won't be running a single A unit on a train, or a B unit next to the train, the Unimates work just fine.