Thanks Danny. The Maxey Papers appear to be the best bet. I have copies from the Maxey Collection I obtained from Gilcrease in Tulsa but there may be more at Austin.

Oklahoma folklore says the 20th Texas was at the Battle of Middle Boggy in the northwest Choctaw Nation, Feb. 13, 1864. I believe this is an unfounded assumption based on the Union report of Col. Wm. A. Philliips who says the enemy was Seminole, Choctaw, and Texans. I believe the Confederates engaged were members of Jumper's Seminole Battalion and Reynold's Chickasaw Battalion. Either of these may have included 'Texans' or at least whitemen (i.e. Lt. Walter Martin of the Chickasaw Battalion -- Nail's Co.). The Chickasaw Battalion included some number of Choctaw (i.e. Capt Jonathan Nail, Lt. Silas James.)

It appears at least one company of the 20th TX Cav was at Boggy Depot at this time and Col. T.C. Bass requested a medical discharge at Boggy Depot on Feb. 10, 1864. The battle was about 30-40 miles northwest of Boggy Depot.

I can't find any evidence that members of the 20th TX Cav were at the battle (yet).