I got a math boner reading all this. I can just imagine mapping the trichs in a cool program to tell you where things are at by submitting pictures and matching them up with a big picture of the plant. mmmmm
I ignore popcorn buds whether they are on the bottom of the plant or in the middle. I only pay attention to the buds either in direct light, or the buds that are nice and fat right behind them. I usually look at two or three buds. I try to pick the one that looks the most done, that would be the main cola in a 'normal' grow, in my closet I find it to be usually the bud closest to the light, or near abouts. So I check that one, both the actual bud and one of the sugar leaves sticking out. I then check one of the real nice buds in the second tier that are still a little more glisteny and not so ready looking... check that bud and a sugar leaf coming out.
I kinda take the average of what I saw there and use that as the measure to harvest that plant. I go plant by plant. I like a little more up high so I usually take them earlier than later. If I start seeing amber around it's about time. Even just a few.