Sadly, clustsim cannot be used with less than 14 subjects (or rather, 14 sets of data). Per the
help on down the page:
++ If you have less than 14 datasets total (setA & setB combined),
this option will not work! (There aren't enough random subsets.)
** And it will not work with '-singletonA'.
There are also some details in there about the min per group I believe - if that is important to you as well.