Before revision:  The stretched grid yields c_{4,1}\leq 0.00457936, c_{5,1}\leq 0.000405335, and c_{6,1}\leq 0.0000291323.
After revision:  Our experiments indicate that the stretched grid yields c_{4,1}\leq 0.00457936, c_{5,1}\leq 0.000405335, and c_{6,1}\leq 0.0000291323.