hey bob, glad to hear the grow is still going well. don't forget that there is a measure of personal taste involved in harvesting. You might want to try harvesting one plant in stages so you can check the various stages of "ripeness" and choose which one is right for you. Or you might wait until the meristem bud, the bud on your main cola, is a little more amber while your lowest, smallest buds are still more clear and get a variety of ripeness levels that way. You might find out that you like to have the same strain harvested at different stages for different purposes. Don't get too hung up on rules of thumb and recommendations--use them as your guide. Besides, these percentage estimates are super iffy. Since you don't want to handle the buds too much at this stage, you're not going to be scoping 50 different spots and then actually counting trich heads and then dividing the number of amber, milky, and clear out of the total. You're going to look at 3-5 different spots (preferably at different heights on the plant) and give a ballpark guess based on those 5 samples.
I'd go ahead and give the full 9 weeks before planning to harvest, and then start checking your trichs every two days or so. When things look, smell, and feel (sticky!) the way you want, start your chop. if you want to harvest in stages, start with the tops and work down over the course of another week-10 days. Personally, i like to chop the whole plant at once.
be easy,