Update! -- I found the setting that allows me to change the number of participants in a group! So, I upped ours to 20, which means we can add nine more. Since the new "groups" feature on the site means the group doesn't go away at the end of a camp month, we can continue this group during other camps and November nano as well.

So, if anyone didn't get in the cabin when it formed, or took this camp off but are planning others, I can add you