[Sakai07]

good point, in the early years of WWI the English did paint union jacks on their air craft. I must assume that this was changed in favor of the roundel due to the nature of AA combat. Quick flashes of aircraft flying by necessitate the ability to quickly and accurately identify friend from foe. The confederate roundels should be as different as possible from US planes, and the ones in the pics above fit the bill nicely. just my $0.02!