Note: This document is meant to evolve throughout the planning phase of your project. That is, it makes sense for you to commit regularly to this file while working on the project. Most importantly, it is a reflection of all the planning you've done in the first iteration. This document will serve as a master plan between your team, and your partner.
While you are scoping features, classify them into non-negotiable, nice-to-have, and could-have. This document is will be a rough draft that you and your co-PL will be using to plan out features before you finalize your scope in the Project Proposal document.
Make a copy of this document!