[Superman]

I've got a lot of respect for civil engineers. And wind. If I offered suggestions about diameter and depth, I would be talking out my @ss.

That said, if you could make foundations for 'guy wires,' I suspect engineers might smile upon that. That's a lot of stress at the ends of long posts. If you place enough concrete for the guy wire anchors, then I suppose you could attach them high-ish on your posts.

As I say, I got great respect for civil engineers. Mother Nature is going to destroy whatever you build. It's just a matter of time. Better to overbuild when dealing with her.