It is one of the unique things about fish keeping, there is no perfect way. People have been sucessful using different methods. What you can do and what is sounds like you have already done is think about these different ideas, and then apply what works for you.
I think a 100 gallon tank is perfect, with 24 unsexed individuals. I don't like to ever mix my Tropheus, they are all too closely related, and they will cross. Keeping two different groups in one tank can defeat your purpose of trying to get them to crank out the fry. They expend all their energy on each other, and usually one group become dominate over the other group. The males are so tired from protecting their areas, that they don't have the energy to spawn.
To read more about my ideas and Tropheus you can read this article:
This is a great group of cichlids to work with, I think they are so much fun.