For example, if you have N couples + one extra dancer, use the rotation for N + 2 couples.
(e.g., if you have 15 and 1/2 couples, use a rotation for 17 couples)

Whichever couple gets the 'sitout' has one dancer dance with a phantom, and the other dancer dance with the leftover single dancer. The square with only 7 people can then decide to either sitout or dance with a phantom.