Anyway, once supplies of the original multi-layered and very slightly thicker board material were
re-established, there was less of a need for the spacing washer. However, these washers have
been retained as with the new longer 3/8” posi screws, the fixing appears more consistent and
better.
My strong suggestion is: Firstly when fitting an armboard, and before you offer it up to the subchassis,
is to introduce the screws into the three holes, with the board upside down on a work
surface. Pilot them in to a depth of about 80% of total insertion.