Hi Wingedwarrior,
I have a slightly different order, but of course I could have it wrong...
20. June 1917 from NW to SE:
"Französische Heeresgruppe Mitte"
5. Army - 4. Army - 2. Army - 8. Army ( 8. Army already belonged to "Französische Heeresgruppe Ost" )
At this time french 1. Army was stationed in Flanders together with british XV. ArmyCorps and belgian troops. To my knowledge french 1.Army was stationed there till the end of the first Battle of Passchendaele...
It is possible that the order of battle changed in August/September 1917 but I have no data for that period.
Hope it helps a little bit,
Immo