At what size would you be able to sex champsochromis?

I have an all male hap/peacock tank and have wanted a male of one of these for a while. I have never seen a mature male but picked up a smaller juvenile from RCA a few weeks back. They had some larger 6+ inch ones there but they looked really ragged and so I did not chance it and bought one of the smaller ~3.5-4" examples from another tank. The fish I have is about 4" and I chose (though a lot of it was guessing) what I hope to be a male. The fish I have does have egg spots on the anal fin. Do females of this species frequently have the spots as well? I do not remember the others having the spots as noticeable if at all in the tank I picked from, which is kind of why I went with this fish. There is blue on the lips and a faint blue hue to the sides but I do not think it is more than what a female might be capable of. The black horizontal bar is still present down the side but is kind of blurry and not really dark. At about what size would a male start to become somewhat obvious? I was thinking about 6-7" and have searched the net but have not found much info.