You have to create two projectors in MadMapper and move them to different places (second one on the right of the first one).
Then create twice the 3D surface, once for each projector. Then calibrate them.
That's it !
If you want the projection to be clean from any point of view, you should use 3 projectors, cause with 2, you'll have places where you have almost no definition. But it depends on your situation.
In the best world we would need soft-edge but from my tests, the places where the two projectors overlap was not that visible, and in the worst case, an fade image as another layer with blending mode "Multiply" should be enough.