Greg,
Looking at the garrison flags sizes there does not seem to be much uniformity to the May 1863 flag specifications. While the 10' 1/2 x 20' garrison flag comes closest to the 1:2 ratio ordered by the May 1, 1863 law the other flags fall short of the official specs. The 6' x 9' flag does adhere to the CS Navy Department's order of May 20, 1863 of a 2:3 ratio but that was for naval ensigns. Thanks for sharing this with us.