Kirk "The Man" Douglas (Vikings)
Re: The shift for out of supply unit
Yes indeed this question has been asked and answered.
The defender chooses which hex he wants to use for mods, so if you chose the supplied unit hex, you would indeed be in supply, if you choose the un supplied unit hex for some reason (like you enjoy pain or something like that) you would then be considered out of supply. Basically the defender always gets to choose which hex will be applied for the combat resolution.
Meant to mention this, in your example you are attacking get a CA result, so now you do in fact become the defender and can choose which hex.