You must make a very tiny seam on the circular form! (center to perimeter or from anywhere to the perimeter)
Because form must have 4 "sides" !
So another solution π
here a big one seam! π
But you see easily the "4 sides" of the curvated surface!
https://sketchucation.com/forums/download/file.php?id=146671
https://sketchucation.com/forums/download/file.php?id=146672