I had a breeding group years ago when they were still placed as part of Cichlasoma. I was told and I can believe it that they establish a large territory that is about 2 meters in diameter ( 6 1/2 foot diameter) or larger in which the male finds or places a smooth rock at the middle, cleans it to attract a female and they spawn on that. In the case of the pair I got to spawn the female dug a pit in the gravel right below the rock and once the babies were free swimming she would gather them in that pit for safety.
Hiding places are the right way to go until you figure which are a pair. At that point I would take out the other males so that the pair don't kill the others and the fry will not be eaten.
My pair spawn at around the size of yours but really got it right when the male was about 8 inches and the female 6+.