Nathan, I don't agree with some of your designations of light or heavy stress. (I may have misunderstood them. I use large and small Xs.)
For ex, you have "behind" as an Xx, but I don't say BEhind. (I live in the upper Midwest.) To me, they're equally stressed, or the second syllable is a little stronger. Without looking at how you had it marked, I would have read that sentence as:
She ran behind the counter and picked a vase so big and grand.
xXxXxXxxxxXxXxX
The stresses alternate, starting on the weak stress, with a little muddiness in the middle.
Then began to pick some humans, each meticulously planned.
xxXxXxXx(x)xxXxXxX
I think you could probably do something about the middle of the first line, but I agree that the lines work pretty well--especially the second (which also gets the benefit of the payoff image). But I think they do have meter, and aren't random.
I hope something in that helped.
