Wait, why does it need to be side by side if all they need to be able to do is smell and talk to each other? Because right now I have it side by side, but they can’t see each other.
the cage of a single piggy needs to be next to the cage of others for interaction - smell, sight and sound. covering a divider is fine to use to calm one down temporarily but you would be looking to remove the divider after a time so all senses for interaction can be used. Using stacked cages with a single piggy means the single would not share a dividing wall so would not have full interaction and can lead to loneliness.