Hey Sinister,
I did read that somewhere as well. It said that because they are both a dark blue and light blue in color, the saulosi does not like it and will show more aggression towards the other fish. Unfortunately i found this book after the fish were purchased when I was reading up more on the species. I have to say though that in my tank there is no aggression towards the msobo and the saulosi. If anything both the male saulosi's are in a territory fight with each other on each side of the tank. They seem to work things out though.
Also, I am not to concerned about the fish creating hybrids with each other as I do not plan on selling the fish, it is only for my own personal recreation of the fish. I have been able to notice subtle differences in the female fishes, although they are both yellow in color, they do have different face structures, the msobo has more of a pointed mouth, while the saulosi has a more round mouth. I do think it would be kind of cool to have a hybrid of a saulosi and a msobo.
Thanks for getting back to me on the holding tank and on whether or not I should remove the fish or not. I will keep her in the tank until I see signs that she is holding and then go through the remarkable task of removing the rocks from my tank to retrieve her.
EDIT - On a side note, do you think that this will help the female in keeping her eggs and not spitting them out early?