[john70t]

Sheer strength of the posts will be a problem with 60' and 8' high.
High winds would knock the entire thing over like a sail, if just bolted to the top of a sonotube.
(Unless triangle-braced. Which would look ugly and take up space. Those could be the ramps to allow flowering vines to creep to the top and along it though)
Probably need 4x6 or 6x6 posts, or maybe every other one even larger which would break up the long surface visually.

The 'hack might be to embed a steel 'T' into each pored sonotube and brace in place while drying.
That would bridge the strength gap between pillar and post.
It seems difficult, requires precise laser measurements to the 1/4", easy to screw up, and would not be as strong as a single piece of continuous lumber.

Another hack might be to waterproof the outside of the sonotube and put one of those round skirts around each base. The rain is shed outside of it and doesn't even get to to the porous concrete.