I'm making Barbara Kafka's simple roast turkey, but my turkey is 16.5 lbs. How should that impact the cooking time?

This is my favorite bird-cooking method. One of our editors, Lindsay Jean, posted a great answer to a similar question here: https://food52.com/hotline/29874-we-bought-a-20lb-er-wanted-to-do-the-high-heat-method-but-read-we-shouldn-t-wanted-a-back-up-plan (There's a bit more color from Kafka in here, as well.)