4 1/2" x 7' Fiberglass Pipe Post, Fiberglass Pipe Posts are probably the strongest, longest lasting, most economical, permanent posts you will every buy! Not a wood composite. No ruptures. No shorting to the ground. Designed to last 30+ years, no need for extra insulators.
In the additional pictures you will see that we use a Hammer Driver hooked to the 3 point and hydraulics off the tractor. They are driven 3 to 3 1/2' into the ground leaving 4' above. The 4 1/2" post have held up very well even in our rocky conditions. We chose to "H" brace them with our 2 1\2" post (FP2.5x7). To hold the "H" in place we drilled holes and put in and "L" shaped homemade pin as seen in the pictures. We then ran support wires from corner to corner and tensioned with an SDS tensioner. We put screws in the bottom of the 4 1/2" put to keep the wire from sliding up and it is rested on the pins to keep from sliding down.
This is a very sturdy corner.