These are all the safety pilot rules, from the rule book.
4.3 Competitor Qualifications
4.3.2 Competitors or their Safety Pilot must meet legal pilot certification requirements appropriate for their
aircraft
4.3.3 Competitors must meet legal medical requirements appropriate for their aircraft.
Exception: This requirement is waived if the competitor flies with a Safety Pilot who is legally qualified
to act as Pilot-in-Command.
4.5 Safety Pilots
4.5.1 The competitor will be the sole occupant of the aircraft during Advanced and Unlimited competition
flights. In all other categories, Safety Pilots are authorized.
4.5.2 Safety Pilots must have aerobatic competition experience.
4.5.3 The competitor has the sole responsibility for determining the qualifications of an individual to act as
a Safety Pilot in the competitor's make and model aircraft. If the competitor is a Student Pilot, the
Safety Pilot must be an appropriately-rated Certified Flight Instructor.
4.5.4 Safety pilots shall not communicate to the competitor nor manipulate the controls during the
Performance, except as needed for safety.
4.5.5 Any figure aided by the Safety Pilot shall be zeroed.
20.2 Order of Flight
20.2.6 Competitors who are also acting as a Safety Pilot in the same category must fly their Unknown Program
before flying as a Safety Pilot for another competitor in the Unknown Program.