Digging up an older thread to ask the question . . .
So it appears most seat bumpers did not survive the test of time. Looking at the pic Barry posted it supports another picture I've seen posted by him of a bumper that did manage to survive. Looking at this installation method intuitively doesn't make sense to me, and leaves little doubt why most bumpers broke. This installation forces the bumper to support the occupant loads placed against the seat back, where the fastener is simply holding the bumper in position.
Looking at the engineering drawing it shows the screw being inserted thru the spacer into the seat back. (photo attached). Additionally the instructions provided by note 9 state to insert E (screw) thru hole in item F (bumper) and threading into the seat back. Installation by this method would support why the screw length is as long as it is. Had the intent of engineering been to install as previously suggested by this thread the spacer would have been drawn above the screw and the instructions would have stated to insert item E (screw) i
nto bottom of F (bumper) . . . and the screw could have been much shorter in length.
Doing as instructed by the engineering drawing would make the bumper/spacer intent to eliminate the metal to metal striking of the screw on the seat bottom plate, a spacer for setting the screw depth, and a more appealing close out to a screw being exposed. The screw would then be used to support the forces created by the occupant and would have only a small piece of nylon extending beyond the screw head acting as a spacer and strike guard. In the event the spacer/bumper were to fail the seat back would still be supported by the fastener.
So where all bumpers installed as shown by this thread or was this simply one interpretation by a line worker.
Thanks for the input.