My build manual shows and car (1998) had a steel washer next to the A bracket followed by the nylon 'race' washer next to the DD Tube, same on both sides.
If the washers are not fitted then I would think that the A frame tubing will bend when tightening the nut.
As I understand it, for my car at least, is that the steel washers are essential and the nylon race washers are optional. The steel washers butt onto the central tube in the bush on either side and are clamped by the A frame.
If you need the washer dimensions I can get them in the morning.