How many Cichlids can we add this weekend?

We have a stable 29 gallon tank with 5 small (1.5-2 inch) Cichlids in it at the moment. We've had them for almost 3 weeks. We did have some issues and had lost a few of our original batch but have had the tank stabilized for over a week now. We want to add a few more fish to the tank. The ones we have will of course grow more, to about 4 inches but we have been told that we should overstock a tank with cichlids because they do better in such environment. So we where wondering how many cichlids would we be able to add this weekend?