as I previously wrote, we're using https://specs.interpeer.io as the home for our specifications now. The first draft is now sufficiently complete that feedback is welcome; you can find it at https://specs.interpeer.io/draft-jfinkhaeuser-vessel-container-format/

Note that the corresponding code project at https://codeberg.org/interpeer/vessel does not yet implement the specification; rather it provides a starting point. Finishing this implementation my focus for the coming weeks.