Have you researched the Supplement to the 'Official Records'? It will have the month to month Event Records that tell what each Company did and where they were at.
I have not found the Supplement on-line anywhere, but several libraries have them. They are a set of black books that were made after the original 'Official Records' were out and give additional information not in the first set. It also gives the Events Records of all of the Regiments and Companies.
Did you order his Compiled Service Record or did you have access to the microfilms? There are actually 3 different sets of microfilms that you need to go through to be sure you have all of possible papers. (The service records are separate and different than the Pension File).