  Using ideal and viscous hydrodynamics, the ratio of azimuthal moments
v4/(v2)^2 is calculated for pions, protons, and kaons in sqrt{s}=200 A*GeV
Au+Au collisions. For any value of viscosity here is little dependence on
particle species. Ideal hydrodynamics and data show a flat curve as a function
of pt. Adding viscosity in the standard way destroys this flatness. However, it
can be restored by replacing the standard quadratic ansatz for delta f (the
viscous correction to the distribution function at freeze-out) with a weaker
momentum dependence.
