I have a 3' 29 gallon tank that has 7 yellow labs and 17 pseudotropheus demasonis. They are all different sizes as the spawnings have raised thier numbers. There are also two albino plecos in the tank for algae control. I do a 75% water change religously every single week to 10 days.
Conventional wisdom would say that this tank is way overpopulated. However, it is stacked to the top with a wall of Texas holey rock in the back and I have provided a nice little cave for each and every one of the fish, with several more that seem to "rotate occupancy". (Two years ago I started out with just a trio of labs and six demasonis....they keep multiplying! In the past two years I have been able to grab some of the fish out during feeding time without taking rocks out and dismantling the entire aquarium. My guess is that I've removed at least 15 fish during that time period and re-homed them to the local fish store).
Anyway, I haven't lost a single fish. They are happy and reproducing steadily.
If you provide enough filtration/water movement as well as plenty of hiding spots, you can successfuly keep a very high bio-load in an aquarium if you are willing to keep the nitrates under control with frequent water changes.
29g is pushing it but it you want to try, Afra seem like worth the effort. Afra have Mbuna attitude but without so much violence. I'd give it a try if you already have the 29g.
Long term, who knows, but then you may be bored with the setup after a couple years anyway. I'd start by trying to be somewhat crowded, then maybe thin out if you have to.