They are just testing your patience, so don't give up. When trying to get two of this species to pair up, beware that the males are real abusers. You are right to have plenty of cover for the young females, and subdominant males. If you ever notice them up in the corners, remove them immediately, because they won't last long. If the female isn't cooperative he has no problem killing her off.
Territory is probably the most important factor to stimulate a spawning.
Sometimes it is easier to breed them in a community setting for this very reason. The males aggression is channeled away from the female, because he is defending a territory. I had this one pair, and the male would just trash the female. Gary would remove her in the nick of time, nurse her back to health and throw them back together. They would spawn, and then he would try to kill her again.