Correct bolt and correct depth nut?
I am reading this with interest as I am currently stripping and rebuilding a couple of MB mk 9 seats from a Harrier for a museum.
I have, tonight just installed the shackle bolt which does have a shoulder. This means you cannot over tighten if common sense were applied. If I were to use another bolt with a shorter shoulder it could easily be clamped, rather than a loose fit. If however a nut that perhaps had a counterbore on its inside or indeed was over tightened, I would say that would also cause an issue. It is interesting to note the comment that the correct bolt has a short head. This is true for the Mk9 seat and you simply use a cranked ring spanner. If you lift the scissor shackle up it really is not an issue to fit a spanner.
Regarding torque settings, I will check the manuals that I have and report back.