Thanks guys.
I'm still back using Sonar 5 with basic tracks and bus support. Not sure I'm aware of Channel tools being in S5....will have to poke around... I was a bit surprised at first that I couldn't just select a mono track to be played stereo (have the mono track sent out both sides) into a bus where I could then flip the phase between the channels. But this doesn't appear supported.
As I said, the split/phase approach is just one aspect, not the whole procedure, for creating a stereo image. There's other overlays that happen so having things disappear is not going to happen. Even so, who in the world is going to listen to something in mono these days? That's even less likely than somebody still running XP and S5 like me.
Sonic