16 gauge will work until you get a strong wind then they will fold over. My father in law (rest in peace) had the perfect solution. He put 2 7/8 posts in the ground to just above ground level. Then took the 16 gauge post and slid them inside the 2 7/8 post. When a major storm happens the post would lay over. He kept a spare 16 gauge post for just such a purpose, took the section of fence off, replaced the post, put the fence back up in no time. The 2 7/8 pipe was drill stem he purchased and cut to length. Works great for many years.