the april date for William Cabell would seem to make it unlikely that he ever served with the 4th State troops.

When war between the States became inevitable, Captain Cabell removed to Fort Smith, Arkansas, and from that place sent his resignation to the War Department, D. C. Then he went to Little Rock, Arkansas, and offered his services to the Governor of the State. On receipt of a telegram from President Indicates a West Point graduate and gives his Class.Jefferson Davis he left on April 12th for the seat of the Confederate Government at Montgomery, Alabama. Captain Cabell reached Montgomery on the night of April 19th, and there he found the acceptance of his resignation from the United States Army, signed by President Abraham Lincoln.

http://penelope.uchicago.edu/Thayer/E/Gazetteer/Places/America/United_States/Army/USMA/AOG_Reunions/44/William_Cabell*.html