hi Jaron,
consider this post: Integration with DIABLO for N-ingretaion with low sample size
Basically, you can choose an exploratory analysis (no cross-validation, just data mining), or use leave-one-out with caution in your interpretation. It all depends on what you say about the results that really matters.
There is not set formula to define N, it depends on the number of datasets, the variation and noise, the separation between sample classes …
Kim-Anh