  We experiment with several new modifications for the
Baumgarte-Shapiro-Shibata-Nakamura (BSSN) formulation of the Einstein field
equations and demonstrate how these modifications affect the stability of
numerical black hole evolution calculations. With these modifications, we
evolve both single non-rotating excised Kerr-Schild black holes and punctured
binary black holes, and obtain accurate and stable simulations.
