Key on that, or each successive layer will be out just a little more. By the time you get up to 4', it'll be out at least a couple inches. If you're going to have a lean in there, have it going the other direction.....toward the rest of the stack. Or, just use posts.
Yeah...probably will try this one more time. If I can't get the hang of it I'll just go back to posts. I don't use a lot of wood so I don't get the experience needed to do a good job.