My old boss told me to always use 4x4 posts for a 6 foot privacy fence, no matter what.
He said it was the only way to make it last, and I did it that way for years. Then I started my own crew and a soil guy in Austin looked at one of my jobs and just laughed. He said in our clay soil, a proper 4x6 concrete footer with a 4x4 post set in it is way stronger and stops the heaving that cracks the concrete. I tried it on a job last month, using his specs, and it was rock solid after that big rain we got. Saved on lumber cost too. I feel dumb for not questioning the old way sooner. Has anyone else had a soil expert change their basic post setting method?
Ever had a boss who pulls that? Mine would just say "not in the budget" and walk away. Best thing you can do is get a quote in writing from the Austin guy and slide it across his desk. Makes it real and harder to ignore.