With the new hinge halves on the bottom edge of the seat back, the
middle eyes need removed (again).
...all tidied up.
Near the center of the three hinges, there are some rivet locations which are
close to a rib. It appears the shop heads of the rivets will interfere with these
rib flanges.
Having marked through the holes, then removed the seat floor, this shows
where the interference will be.
...so I just filed the edges a bit to provide clearance for those shop heads.