I have read some hints that the the cross on the Army of the Potomac's 6th Corps division and brigade flags changed at some point. Am I correct that when first issued in 1863 the cross was an upright Greek cross, but at some point in 1864 it changed to a diagonal Andrew's cross?

Also, it appears as if the corps flags (of all corps in the AotP) were changed on August 1st, 1864 in both size and appearance. Prior to that date, the flags were 3 feet by 6 feet, and had the red numeral in a white tunic cross. After that date, the corps flags changed to 2 feet by 6 feet, and the tunic cross was changed to the corps symbol. Is this correct? Would this have been the date when the 6th Corps cross changed from Greek to Andrews?

I have one book that states the August 1st changes was issued in General Order 115, but I cannot find that order anywhere in the Official Records.

Thanks!

-Brad