One thing to keep in mind is the SCHOOL effect. I visited Don Conkel on vacation last year and he told the benefits of growing cichlids out together when they are very young and small. He said it creates bonds and a pecking order, much like in a school of fry. When they grow up together they are less likely to kill each other, but anything is possible. At 8in your festae are pretty much considered ADULT which makes adding fish a crap shoot. This makes them way more territorial to a new fish as in comparison to growing out the festae and geos, sevs, etc. from say 2 inches up to 8 together. Ever since he told me this, I've tried it and its basically worked for me and I thought back to all the times I lost a fish when adding them in at over 6 inches. If you had a 500 gallon plus tank, things might me different. When you set up your fish room try starting a group of different cichlids in something small like a 40/55 and move them up and you might get better results.
From DJ/MC Decker
From DJ/MC Decker