I use a full quarter inch seam because the ones I have done have the points on the end and need the extra stability. I, also, backstitch at the end of the seam where the sides finish near the pointed end. I have no idea how many you will need. That will depend on how wide they are and then I still wouldn't know. A circle is 360 degrees. Measure a finished size of yours, on a circle to find out how many degrees wide it is. Then divide that into 360. That may tell you. Be sure to keep your seams exactly 1/4". I had problems because I was tailing off at one end and mine wanted to cup up. A lot of resewing involved....haha