I may overlooked the Carruth letters or just didn't get the right term, but I did not see them.
I was able to relocate the Rankin and Pittman letters, so I am sure I wa in the right place. I saw a couple of hits using "7th Miss." as a search term. If you would check that out and let me know if we have those manuscripts.
Jamie In Civil War Collection, I saw a Roberts with some letters. I believe he served in Stanford Battery.