My seats have been recovered without headrest holes so made up some tubular brackets, bolted them to bulkheads behind seats, slotted in headrest. Think they are now much stronger then the tubes inside the seat backs.
You may need to put your hand up the inside of the back of the seat cover, there should be two push in clippy things that fit into holes in the tube. Is the passenger seat not open backed?
I’ve got two driver’s seats, none of this foldy stuff I’ll let the trimmy man wrestle with the bezels.