This is interesting.... Can a person not book two cabins??? Can a name not be on two cabins? If they are paying for it, why not... You can have more than one cabin on deposit, right?
Either way, if two couples or a family or group wanted an extra cabin, then they will, of course, pay for two passengers in the extra cabin. So, these four people would be paying six fares, no matter how they arrange the booking.
ecs66, I do have another thought for you, if you wanted to contact me.
( I grew up just up the Hwy from where you live!!! )