Exponential correlation decay for planar Sinai billiards with corner points

Consider planar Sinai billiard flows whose boundary may have corner points, with the angle between the intersecting boundary pieces at each corner nonzero. Corner-point correlation-decay conjecture. The main result on exponential decay of correlations for planar Sinai billiard flows remains valid for these billiards with corner points. The claim is motivated as a necessary step for controlling correlations in the cited heat-conduction model; the supplied context gives no resolution.