In re-reading your post, and looking again at Rollins' book, the 12th Alabama is also possible, although why he leaned away from that ID and went with the 26th (and mentioned the 6th as a possibility) was probably because the 88th PA mis-identified it as the "16th" and therefore went with the two regiments with a "6" in their designations.

How does the 26th's flag being taken change the O'Neal alignment? Rollins has the 12th on the right, 26th in the center and 6th on the left with the other two regiments being out of the fight based on their position.

Greg Biggs