I think you'll want a t-post at every panel join on the straight runs, and maybe every other one around the ends. Used ones go for about $2 around here on Craiglist or at auction.
A friend here has an arena very much like the one you describe, all made of 12' panels. He's used it for over 15 years for roping and sorting.
How's Mesa?
A friend here has an arena very much like the one you describe, all made of 12' panels. He's used it for over 15 years for roping and sorting.
How's Mesa?
