From: Nepean, Ontario
THe real main concern for good supply is keeping to HQ's, all levels, on connected rail lines. Corps HQ's should stay within 8-10 hexes of their Divisions to make sure they are giving full combat bonuses.
Army HQ's and higher just need to maintain a clear rail line path to their lower HQ's. THis can mean rearranging commands or the locations of the group HQ's.
Also note that in Case White the Polish rail lines take a turn to become useful by the Germans to simulate the need to change the rail gauge.
Life is not a journey to the grave with the intention of arriving safely in a pretty & well preserved body,
but rather to skid in broadside, totally worn out & proclaiming "WOW, what a ride!"