@Jxrc: While that's admittedly bigger than I usually see the Byzantines become, it's definitely not unheard of, either. In any case, though, Caliburn is right -- it's usually only a matter of time before the Byz begin to shrink and collapse.

Your safest bet may be to simply wait them out. Sooner or later they'll begin to contract (the Horde should help that along), although it may not happen until you're into the High period.