The little wheels that come with the circle cutting attachment left a lot to be desired, so I made this.  The plasma head fits snugly in the bore, eliminating the need for setscrews, and I just drag edge of the adapter along a straight edge.  I couldn't place the axis of rotation right over the nozzle, so there are two different offsets I need to use depending on if I am beveling left or right, but it works for its intended purpose, which is to make compound miters on rectangular tube.