I've found my weakest link.
You've heard the old adage "Measure twice, cut once."
Mine is "Measure twice, send the wife to Lowe's to get more lumber." I somehow ended up short on one of my post. It was a center post and my end post are still square. I had to do a quick fix on the fly as I was not about to pull the post and reset it.
Tommorow is siding day. I can't wait for the fun to begin.