I'm fiddling with the motor calc spreadsheet but the stepper specs don't give me the rotor inertia or the detent torque. Is it something that can be calculated or is there a fairly safe estimated value I can put into the spreadsheet to keep me in the right kind of ballpark?

It's 60BYGH301B [link to PDF], the Nema 23 3.1Nm from cnc4you.