Hey folks.

I'm a bit confused about how a corpse cart would displace models within a unit, because of its odd basesize.

Heres the situation:

I have a unit of twenty ghouls, for the purposes of ghoulkin i place a corpse cart (with a necromancer on top) within the unit.

For ease, i just slot the corpse cart next to the unit, the corpse cart displaces around 8 ghouls. Like the diagram below:

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Now, it starts to get confusing when the corpse cart leaves the unit. While none of the ghouls actually move to incorporate the corpse cart (because the corpse cart effectively takes the space of 8 extra ghouls, making it a 7x4 formation), do the ghouls have "reform" after the corpse cart has left the unit to make it a 5x4 unit?

I don't have the rulebook near me to check it, and its starting to boggle my brain.

If the corpse cart leaves, does the ghoul unit become like this:

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OR does it become like this:

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Formation one: the ghouls are actually moving, in the second formation none of the ghouls actually move. But formation one is keeping the same formation as the original unit!

This might be a reallly noobish question that is easily answered, but without a rulebook this is becoming hard for me to get my head round.

The question in short is this: Hows does a corpse cart interact with ranked up units?