Section 5.e, "
Safeword" talks about calling safeword but doesn't say what the safeword
is. I'd suggest a sentence which says that a safeword must be chosen by the Master and communicated clearly to the slave.
There are common (and delicious) situations in which the safeword can't be spoken or heard. Normally it's understood that some non-verbal safeword is used instead—"To call safeword, pull your right leg against the restraints three times in a row, then left leg." A clause requiring this would be appropriate:
If either Master or slave is about to be in a position where the safeword cannot be communicated verbally, the Master must choose and clearly communicate some nonverbal method of calling safeword to the slave before the verbal safeword is impaired.