Fiddly bits

So much for using two washers between MDF surfaces.
Instead, I now have one 8 mm washer (wider) between the stage and the pivot bar, but two 5 mm washers between the MDF and the PTFE, which prevents the disks from rubbing against the MDF where the disk thickness isn't perfectly uniform. In order to fit the extra washer, I have had to swap the disks' screws to the 3 cm length. I now have freely spinning disks, but the pivot bars are not so free. Net result, though, is much less friction.
One advantage of the extra washer is that the disks are now better aligned with the rail when the PTFE slide raises the x-stage slightly above the rails.
Now to sort out some feet for the assembly, once I know how much drop I need for the motor.....