With Africans yes but not in a 29
With CA/SA not ever unless your awfully lucky. I personally tried to do an overtocked tank experiment. I got all the fish at .5"-1.5" and grew them all out together. By the time the fish matured in my 265 gallon tank, overstocked or not they didn't get along. It was a very stressful situation with all the constant fighting and fish were dying. Another issue was the water quality suffered horribly. I had to do a 50% water change twice a week to keep up. I'm glad that experiment is over. I sold more than half the fish to my lfs and kept only my fave's.
A pair of Sajica or HRP might be a nice choice for your tank btw. GL