If a unit is, say 5X5 and I have full command and 3 heroes is one of those heroes displayed to the rear rank or can I move part of the command group to the 2nd rank.
I believe the comand group allways stays in the front rank, but you could make the unit 6 wide if you wanted.
In the BRB, under the unit section it states that the command group must always be in the front rank unless there is no room. (the only way this can happen is if the unit is 2 wide i think). In the character section it states "Rank and file models, except for the command group that must remain in the front rank.... to make room for the characters" HOWEVER, BRB (pg 100) states under "Make Way!" that once in combat, the character can be moved to the fighting rank. It states "You can exchange him with rank-and-file models, including the command group, that are in base contact with the enemy" One thing to note: this means you can replace any model in the unit EXCEPT other characters. So if your mage is in combat, he's stuck in combat, but the musician can be pushed back to make room for the fighting character. TL;DR = The character must be in the 2nd rank until close combat where he can replace the command group