  We present a new choice of initial data for binary black hole simulations
that significantly improves the efficiency of high-spin simulations. We use
spherical Kerr-Schild coordinates, where the horizon of a rotating black hole
is spherical, for each black hole. The superposed spherical Kerr-Schild initial
data reduce the runtime by a factor of 2 compared to standard superposed
Kerr-Schild for an intermediate resolution spin-0.99 binary-black-hole
simulation. We also explore the possibility of delaying the transition from the
initial data gauge to the evolution gauge, which produces an additional
speed-up of 1.3.
