I would do the whole car, and then start removing it on the first panels you applied it too. You DON'T want to let #16 cure too long, and you DON'T want to let the sun bake #16, and you DON'T want to apply it to a hot surface, and you DON'T want use it in high humidity.
We used a lot of #16, and #19 years ago. The #16 really is a nice, durable wax! However, it can be a bit "finicky"! A pro detailer doesn't have the time for "finicky" products! However, if done properly, and used under the right conditions, it should work fine for you.