Washers were put on opposite sides because of the mysterious offset between the brackets on the Y-bed and the brackets on the Y-idler. I used 3/8-inch long aluminum spacers, filling the remaining gap in the mounting brackets with two flat washers placed on the side opposite from where the two washers were put on the Y - idler. Similar to what I did on the X axis belt, I wrapped the Y axis belt around some aluminum spacers and doubled up on the zip ties.
