Hi Folks,
Spent some time and compromised by setting the canvas mode to 'world' and then adjusting the canvas size to match up with the 2dTK camera. I lose the ability to add/edit lines in the Unity editor but for now that's not an issue for what I'm after. Since the lines are part of the game world I wanted to use the same co-ord system which this seems to allow. In fact this allows to make a Unity UI in general scale using the 2dTK scaling as well which I've been wondering how to do as well.
All I did was set the canvas rect transfrom position to the same pos as the 2dTK camera, set Z to something higher than the 2dTK camera Z and width and height to the 2dTK screen extent width and height. Be interested to hear if anybody else does this kind of thing and how they have approached, cheers.
Pete