Instead of enforcing a strict round-robin selection of Bridge Trolls for signing and transaction creator, a rule stating that a Mean troll must have a gap of at least X transactions before they can be transaction creators again serves as a fuzzy round-robin that provides flexibility for unavailable Bridge Trolls. (i.e. if the total number of Mean trolls was 10, this X could be set to 8 to enforce a type of fuzzy round-robin).