interaxial distance for landscape

To get all of the image behind the screen, the ending separation between the image objects that are furthest way, should be around 2.5" apart and the nearest have no separation--they will be right at the window. That said, I don't think you have to worry as with a drone, you can't separate the cameras far enough anyway to create a depth issue. It's probably trial and error. When the cameras are separated more than normal eye separation, along with the wide angle of the lenses, you will get a miniaturization effect. So you have to consider that as well. If the separation of objects on your 2 meter screen are further apart than 2.5", your eyes will turn out slightly creating eye strain especially if you are sitting within 10-20 feet of the screen. Sitting further back will elongate the depth as well. Sitting closer will compress the apparent depth.

There are mathematical equations that can be used, but you really don't know what you are dealing with given the wide angle of the gopro lenses regardless of what FOV you have it set at. Sooo...I think you just have to experiment until you get it to look right. Have others see the results as well. What's good for you, might not be good for others, especially children, whose eyes can be closer together.

You don't have to drone your cameras to get this right.  You could stand on a hill or in a two story building and take some landscape video and try different separations--of course you have to have objects between you and infinity to make this work properly.