If the cofounders have only known each other for about 1 month, what can we do to reassure YC we'll work well together?

Would evidence of some random (yet to be done) side project help? Good chemistry in the video? Anecdotal evidence that we've built up trust and a good relationship? Good legal framework?

We are still actively building a larger team of course but these things take time. This is the only part of the application that worries me. =)