What Ive found in my own backyard is 4x4s work fine as long as you have 5' in the ground. 6x6 are a bit expensive. The orange sales 4x4x16--tis what I used. I also rented a 12" auger to make getting thru the red clay down here in GA a bit easier. I set the post 18' apart and have 10' of post above ground. Happy hanging!
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