Your interpretation of the wording of Douglass's letter is pretty much in line with the way I had interpreted it. It doesn't say Guitar or the other captains are disloyal, but that their companies are composed largely of men who are regarded as disloyal. As far as a specific citation, currently the letter is in Box 26 of the EMM records, 61st Regiment, the Regimental folder Correspondence--Personnel. That citation will ultimately change, when I complete processing the Adjutant General Records for the Civil War. They are currently available for the use of researchers.