This first picture shows the stained glass pieces that I started with. These are all Kokomo glass.
The first and most important thing to do is to make a good cylinder. The ends are not important at this point, just try to make the cylinder as concentric to the mandrel as possible.
Now I've rounded over just the left end. You want to bring the glass almost to the mandrel if you want the ends of the tab to be fairly small. By fairly small, I mean that there isn't a blunt end on the tab.
Now, both ends are rounded over almost to the mandrel, and the bead given a pleasant, smooth shape end-to-end. By changing the shape of the bicone, you can affect the bead. For example, making the bicone larger on on end will result in an almost heart shaped tab.
The finished bead. It is 1" wide, and about 1 1/8" long. I mash the hot glass using my marver, and a 6" square graphite pad. Be careful to not mash too much, or the glass will be so thin across the mandrel that you might break it removing it from the mandrel.
If you mash the bead really flat, you'll get the round shape like on the left. If you barely mash it, the shape be be more elongated like the tab on the right. The ends on the bead on the right should have been smaller. This is what happens if you DON'T bring the glass all the way to the mandrel when you are rounding the end over. Please excuse the fingerprints on the left bead, apparently Vivian has been fondling them
I hope you find this useful. Please don't hesitate to ask questions if there is a step you don't understand.
PS - I'd be more than happy to show anyone this technique. If you are ever driving I-75 through Gainesville, make arrangements to stop in sometime !!