Depends on which type of African cichlids you like. There are about 1,200 species of fish in the cichlidea family and most of them are found in the Tanganyika and Maliwa lakes
The tall tank would definitely limit you, Neolamprologus multifasciatus would be perfect for a tank that size. Since their pretty much bottom dwellers you would lose the top half of your tank. check here for other shell dwellers if your interested. the gallery will give you some set up ideas.
If it didn't have to be africans, a couple of angelfish would be perfect,
Cichlids are kinda hard to tell with. Its better if you have long than tall. I have a Venustus cichlid in a 20gal long and he loves it. So it probably depends on your fish.
That's why I suggested angels, they need a deep tank
like the other have said a 35 hex tank is going to have all of its size in height. the base will be pretty small so I think you will run into problems with most cichlids. your best bet would be the angels or maybe some rams, or even kribs. other than that I think you will have all your fish on the bottom of the tank and wasting all of the height you have,