Hassibi, Hochwald, Shokrollahi and Sweldens (see tech. rep., Bell Laboratories, Lucent Technologies, 2000) classified all finite groups of unitary matrices with nonzero diversity product. It is well-known, however, that differential space- time codes with vanishing diversity product still can perform reasonably well under certain conditions. We show how to compute parameters of finite groups crucial for their use as space-time constellations, using only the character table of the group. Simulations are given for the group SL(2,17)