It's going to be 5' wide by 15' long. The 4" black steel pipe is quite ridged and it would be 2 of them. How much flex is what I don't know. I'm not as worried about the concrete bolt anchoring system as I will make it beefy with re-bar and all that with a concrete tail in the footer. No posts. I have 4 28' steel light poles that go from 2.5"at the top to 6" at the base. One I used as a 25' commercial flag pole. Very ridged at that length. For this I was going to use 21' black steel pipe from the plumbing trades.
