Their are only a few rules to position battles.
1. you cannot challenge a opponent who has not held their rank for over a week.
2. Fights hold rules similar to that of IC battles.
3. If the challenger loses, they may not challenge anyone's position for a month.
4. If the challenger wins, he may not be attacked for a week.
5. Position battles may go on as long as they have to.
6. Once engaged you are not allowed to exit the topic.
7. Once the topic is made you must notify the opponent via PM and they have 72 hours to respond.
8. Any arrancar can challenge any Espada spot.
9. Any shinigami can challenge any Captain for his position.
10. Your character does not die IC if you lose a position battle, they are just demoted.