Unhappy that the length-wise seams of the tube were not perfect, I consulted my friends at the atm workshop, who came up with the following solution. I took a four-foot long board (beech scrap I purchased for the purpose from a hardwood dealer in the suburbs where I also bought some plywood for the mount), 4” wide and ½” thick. From that I cut 16 slats, ½” wide and 1/8” thick. These slats I glued in pairs, one slat slightly overlapping the other along the seams of the tube. The sharp angle thus formed I sanded smooth.