For rafter tails on a purlin system, I have used a combination of purlin and short rafters set into the bottom purlin, the rafters plugged into the purling and run four feet to the plate then gave an over hang with exposed tails outside the building. Here we are pre cutting them in the shop. Possible idea for the tails and at the same time using a principal rafter/purling roof system.
https://www.youtube.com/watch?v=zRsWoUKg8to