This way gives a result that looks well from all directions, without the widow's-peak points:

With some simple UCS adjustments, draw the four Arcs [white] around a square [blue] with a Point [red] in the center, and JOIN the Arcs into a 3D Spline.
LOFT in Surface mode from the Point to that Spline [second item in the image].
Center that on the pipe [green] as in the fourth item with the tutu, and SLICE the pipe using that Surface, and keeping Both sides -- move one of those away from the other [fifth item].

The Arcs used for this are less than full half-circles [I tried that first, but the results looked too "extreme"] -- their rise is not half but 3/8 of their base. You can fine-tune that as you prefer.
Kent Cooper, AIA