Just go to your local hardware store and get some grade 8 washers. Not to take $$ out of Andy's pocket, so buy his excellent book with the cash you save.
We tried washers and the OD is too large so I had thick spacers with the correct OD made. We used them on Tim's Valiant and they worked so I just had some extras made and put them on the shelf. I only sell a few sets a year so it isn't much of a money maker but they don't take up much space on the shelf and they don't go bad over time so I keep them in the product line.
