FYI, the .005" per cc is for SBM open chamber heads. .006" or .007" per cc will be about right for these closed chamber. The 'cut-per-cc' rate won't vary all that much in the range of a .020" cut.
I'd mill them if lower RPM torque was the issue but not worry as much if peak HP is the issue. Since these are the first of these purty new shiney things, I would actually not mill them yet, run as is, and see if the outcome is satisfactory. Then mill them if the low RPM torque needed some help.