Waves UM or TC Unwrap

Anyone tried to use Waves UM or TC Unwrap to take a stereo mix to surround? When I insert these plugs on the Surround Bus, the plugin ouputs don't seem to get mapped to the surround bus - I think Surround Bridge is seeing the Stereo Input and thinking it somehow needs to add 5 plug, when one is all that is needed. At any rate, doesn't seem to work unless there is a trick I don't know.