Continued trimming the forward end of the bubble. Cut two more 1/4" strips from the bottom.
Today I developed a cutting method that leaves a relatively smooth edge that requires minimal sanding. When I made the first cuts a few sessions ago I cut through the plexiglass in one pass. That made it a little hard to control the direction of the cutting disk and caused the bubble to pulsate. The result was jagged cuts that had to be smoothed with the dremmel sanding drum. Today I found that I could work in short sections of a few inches each and make multiple light passes along the cut line removing just a little material at a time. It would take four or five passses to cut through. This method worked much better and resulted in an edge that just needed to be sanded with the belt sander and then polished with the scotchbrite wheel.