The two centralized overlays, CentralizedIndex and CentralizedStorage, are only implemented for testing purposes. Therefore they are not very well tested and should not be used in productive scenarios. If you want to run evaluations with centralized implementations you have to build your own overlay.
Nevertheless, they should run without exceptions. There was a small error in the size calculations as the messages need no receiver (it is always the known server). I’ve just fixed it and committed the changes.