Yeah this thread is old as dirt, but...
An odd dynamic I've seen with FHs is if the female is near or equal in size to the male she tends to shred or dominate. I've often wondered why people paired full sized males with 'barely legal' females...this is probably why. A guy who used to own a family buisness fish store in the neighborhood said that had been his experience. Thing is there's no way to know how big the pairs will grow!
That, and an equal or close to equal sized female FH will often refuse to spawn with a male, that she feels does not qualify as being impressive enough. That often ends up with one, or both, fish getting torn up.