It took a few iterations, but I did it.
My main standing desk is 60″ by 30″. It’s built on wheeled wire shelves. I tried using a small standing desk from Amazon, but it lacked the structural integrity to hold the monitors still while I typed.
What I wound up with is another set of wheeled wire shelves, 36″ by 18″. The top is a 2’x3′ sheet of laminated MDF supported by half-inch plywood. I used a hole saw to notch post settings in the bottom of the plywood. The Mac is mounted beneath the shelf, along with a power squid. My landscape-mode monitors are on the other desk. Each desk is independently powered, but they can be connected with one USB, one audio, and two DisplayPort cables.
Without a better workshop, this design is as sturdy as I can get. The monitors still wobbled. Adding the ten-disk tower PC to the bottom shelf as ballast sufficiently steadied it.
I can now roll out onto the balcony, with monitors optimized for making words. Detroit hit 100F yesterday and 97F today, but I’m hoping for good outdoor writing weather by November or so. January at the latest.
My sincere gratitude to the folks who saw my Amazon wishlist and sent me the parts. Yes, the wishlist is empty–because people keep buying whatever I put on it! Your generosity has made rebuilding a life much more comfortable. Thank you.