Before you go too far down this route, please remember that a stiff nut must be replaced every time it is removed. Tuc has mentioned it earlier.
Like the 1 & 1/2 threads, it is basic engineering practice and written down somewhere.
It is quite relevant for a few reasons:-
1. Probably not mentioned in RTI's and maybe not in AP's
2. Provision of spares for replacing said nut
3.....A stiff nut used several times over would lose its stiffness and could lead to overtightening and 'cutting' an extention of the thread down the shank of the bolt.
Many PPRuNers have been on here expressing their astonishment at seat pin slacktitude. Not many will post saying they haven't re-used a stiff nut