A where we can post settings, so that others can quickly get the exact same thing working in Unity.
Normalized Viewport Rectangles:
Split screen settings for 2 cameras
Top camera - X=0 Y=0.5 W=1 H=0.5
Bottom camera - X=0 Y=0 W=1 H=0.5
Split screen settings for 4 cameras
Top left - X=0 Y=0.5 W=0.5 H=0.5
Top right - X=0.5 Y=0.5 W=0.5 H=0.5
Bottom left - X=0 Y=0 W=0.5 H=0.5
Bottom right - X=0.5 Y=0 W=0.5 H=0.5