Ok, my pier layout has been strung out on site, and I spent some time squaring it up. I love how precise the total station is. You spend much less time measuring and tweaking diagonals when you have a good transit on site.
Now, I've wrapped up enough modeling to be able to quite definitely say how I intend to stay under the County height limit (I'm a bit more than 1/2" shy of the limit, but the shingles will eat up that margin. Any additional overage will need to be accounted for by literally raising the dirt/gravel at the side of the shed.