Manuscript Preparation, Copyediting, and Proofreading
Q. I am editing a military history. The author insists on all numerals for the army units, rather than using numerals for 101 and above. With the exception of roman numerals for corps, is it all right to use the author’s preference?
A. The author is right to use numerals consistently for all mentions of army units. (See CMOS 9.7.) But in any case, when a writer expresses a strong preference for a style that’s reasonable and harmless, there isn’t much point in fighting over it, especially if he has already prepared the manuscript consistently with that style.