Rayleigh-Taylor instability of a laser accelerated ablative surface of a thin target shell with an incompressible fluid saturated porous lining is investigated using linear stability analysis. A simple theory based on replacing the no-slip effect with the Saffman slip condition is proposed. It is shown that the growth rate is greatly reduced over the value it would have if the shell is bounded by an impermeable boundary. This is useful in the very effective extraction of inertial fusion energy.