OP
Thanks.
Today I finished everything off, which is to say I secured it so that when the wind blows, it won't collapse onto itself or sail away.
I hope.
One part of that was drilling several 1" holes in the concrete underneath the thing. I'm always amazed by the effectiveness of my inexpensive Harbor Freight 1" hammer drill when it comes to these occasional holes. The 3/8" bolt you see goes into an anchor that goes 12" down and is encased in expanding concrete mix. It's rated for #2000 of pull. I'm using them to secure one row of the pillars for this thing.
My method was to secure the base plate to the concrete, and then weld the pillar to the baseplate.

