i dont have any knowledge of when you are supposed to start your flush but if you dont want you smoke to be too much couch lock i would maybe feed 1 more overdrive then flush or flush now... BUT like i said i have NO experiance with it... this is just my best GUESS..
i have read the upper part of the plan will mature more quickly since it gets more light but you could always do a partial harvest of just the upper half then harvest the rest when its ready... ive seen ppl doing it and have been happy... but the main reason i wanted to comment was to say good job man