Just at an FYI to the author, this is a bad idea. Once you have left a startup, your opinions are going to be valued much less by everybody still there because, well, you quit. Your incentives are now not aligned fully, you aren’t part of the mission anymore, and this was because you decided you didn’t want to be.
And from your perspective, you quit. Don’t waste your time on them anymore, fully focus on your next project.