Yea I see what you mean, its hard to get the top of the stack very level with uniform height, I tried to tuck the plastic into the "valleys" so it wouldn't rip with snow and ice on it. Should I be stretching it tight?
It's tough to get it to lay flat without something like plywood underneath it. I usually stack in double rows, so I can leave the back one higher, so it has a pitch to it, but even then it's a pain in the neck with the tarps. I scrounged some vinyl siding to use for top cover, but I only have about 1/2 of what I need. So I'm constantly adjusting the stupid tarp.
Some say that cardboard can help on the sub-roofing. I have never tried it as I have a bunch of plywood scraps that I use. Any piece I come by that is of reasonable size gets picked up. As for your overhang, just look at the pile after a rainstorm. (Did you get the rains over the past few days?) If you see wet wood from water running down the face you might want to try and rework things.
