I should add that as a clump increases in size the fans closer to the outer edge of the clump suffer the least from the "self-competition" and therefore should have the "better" characteristics. Given enough time the fans near the centre of the clump can die and the clump becomes a ring. Given even more time, new fans may be able to re-invade the centre of the ring. I have a clump of Stella that had become a ring. It has not been divided in the last 25 years. It took less than 25 years for it to become a ring.
