I did my own expermination, I had 4 cameras. I deleted all cameras from the room view and then re-added. The camera which I wanted iwatchpro to default too, I added first, C4 for me, then I added C3, C2,C1. The pane view shows C4 top left, C3 top right, C2 bottom left, C1 bottom right.
This also solved my iwatchmobile issue, now it always defaults to C4, top left.
Looks like first camera added gets priorty treatment.
Before I did that i deleted my prefered camera C4. It was second camera in pane view at that time. When I added it back it put it as last camera.
hope this helps
ken