I would soon need to glue the seatback locker flanges to the panels, and cut the openings.
I wanted to make sure they were in the right place, but there are no dimensions to follow. As usual!
So I decided where to locate the opening by eyeballing various options until it looked right. I settled on a position where the flanges are 6cm from the seatback support and 6cm from the bottom edge of the panel.
I had already marked in the location of the cleats, supports and stringers on each panel to help me do this, and then I marked in the openings.
Here I am holding the locker flange in place with a heavy weight on the port panel while I pencil in the opening.
That's that done!